Quick Search
Salicylic Acid, also known as 2-Hydroxybenzoic Acid, o-Hydroxybenzoic Acid, ortho-Hydroxybenzoic Acid and CAS No. 69-72-7, is a beta hydroxy acid (BHA) with the formula C7H6O3 that occurs as a white crystalline powder or needle-shaped crystals and is sparingly soluble in water and readily soluble in alcohol and acetone. Salicylic Acid is used as a keratolytic and preservative agent in cosmetic and dermatological products, particularly acne, dandruff, corn and wart products, as an intermediate in the production of acetylsalicylic acid (aspirin) and salicylate esters and salts, in phenolic and foundry resins, as a prevulcanization retarder in the rubber industry, as a coupling agent in azo dyes and as an analytical reagent.
Salicylic Acid is a lipophilic, oil-soluble acid with a pKa of about 3.0 that carries a carboxyl group and a hydroxyl group in adjacent positions on the benzene ring. Salicylic Acid exerts its keratolytic effect by increasing the water content of the stratum corneum, causing this layer to soften and shed, and thanks to its lipophilic structure it can also penetrate into the pores.
Used generally at 0.5–2% in acne products and 2–3% in anti-dandruff shampoos, Salicylic Acid helps reduce problems such as clogged pores, blackheads, dandruff and excessive keratin build-up. In industrial use, about 55% of Salicylic Acid is consumed in aspirin production, 18% in salicylate esters and salts, 10% in resins and 10% in dyes and colourants.
Under the EU Cosmetics Regulation, Salicylic Acid may be used for non-preservative purposes at a maximum of 3.0% in rinse-off hair products, a maximum of 0.5% in products such as body lotion and eye and lip make-up, a maximum of 2.0% in other products and a maximum of 0.5% as a preservative; it is not among the permitted additives in the Turkish Food Codex. Since Salicylic Acid is harmful if swallowed, can cause serious eye damage and is classified as toxic to reproduction Category 2, it should be checked with a TDS and COA appropriate to its quality grade and stored in tightly closed packaging in a dry place protected from light.
WHAT IS SALICYLIC ACID?
Salicylic Acid is a monohydroxybenzoic acid formed by the attachment of a hydroxyl group to the ortho position of benzoic acid. Salicylic Acid is also classified as a phenolic acid and a beta hydroxy acid (BHA).
In nature, Salicylic Acid is found in white willow bark and wintergreen leaves. In plants it acts as a plant hormone that plays a role in growth, development and defence against pathogens.
Commercial Salicylic Acid, however, is not produced from plant sources but from phenol by a method known as the Kolbe-Schmitt synthesis. In this method, dry sodium phenoxide is reacted with carbon dioxide and the resulting sodium salicylate is acidified to give salicylic acid.
Salicylic Acid is available on the market in different grades. Technical grade Salicylic Acid is mainly used as an intermediate in the agrochemical, dye, resin and rubber industries.
Pharmaceutical grade Salicylic Acid meeting the requirements of the European Pharmacopoeia (Ph. Eur.), the British Pharmacopoeia (BP) and the United States Pharmacopeia (USP) is preferred in pharmaceutical, dermocosmetic and cosmetic formulations. An ACS reagent grade is also available for analytical work.
Salicylic Acid should not be confused with its derivatives such as aspirin (acetylsalicylic acid), methyl salicylate, sodium salicylate or capryloyl salicylic acid. Although these derivatives belong to the same chemical family, they differ from Salicylic Acid in solubility, field of use and regulatory status.
Not every Salicylic Acid product on the market has the same technical properties. Since purity, impurity profile, heavy metal content, crystal form and quality standard may vary by manufacturer and grade, product selection should be based on the TDS, SDS and COA documents.
COMMON PRODUCT AND CHEMICAL NAMES:
Salicylic Acid
Salisilik Asit
2-Hydroxybenzoic Acid
2-Hidroksibenzoik Asit
o-Hydroxybenzoic Acid
ortho-Hydroxybenzoic Acid
o-Hidroksibenzoik Asit
2-Hydroxybenzenecarboxylic Acid
Benzoic Acid, 2-hydroxy-
2-Carboxyphenol
o-Carboxyphenol
Phenol-2-carboxylic Acid
Acidum Salicylicum
Acido Salicilico
Kyselina Salicylova
C7H6O3
HOC6H4COOH
Salicylic Acid (INCI)
Salicylic Acid Ph. Eur. / BP / USP
Salicylic Acid ACS Reagent
Salicylic Acid Technical Grade
Cosmetic Grade Salicylic Acid
Some of these names describe the chemical name of Salicylic Acid in the IUPAC and CAS systems, some are its Latin, Italian and Czech equivalents, and others define the quality grade. "Acidum Salicylicum" is the Latin name used in pharmacopoeia and prescription language.
It is important to verify separately, from the product documents, the grade (technical, pharmaceutical, cosmetic or reagent) of products referred to as Salicylic Acid.
CAS NO, EC / EINECS NO AND CHEMICAL IDENTIFICATION
Product name: Salicylic Acid / Salisilik Asit
Chemical name (IUPAC): 2-Hydroxybenzoic acid
INCI name: Salicylic Acid
CAS No: 69-72-7
EC / EINECS No: 200-712-3
Molecular formula: C7H6O3
Linear formula: 2-(HO)C6H4COOH
Molecular weight: 138.12 g/mol
MDL No: MFCD00002439
FEMA No: 3985
JECFA No: 958
ATC code: D01AE12 (dermatological antifungal), S01BC08 (ophthalmological anti-inflammatory)
Chemical class: Monohydroxybenzoic acid / phenolic acid / beta hydroxy acid
Main functions: Keratolytic agent, preservative, anti-dandruff agent, synthesis intermediate, resin component, prevulcanization retarder, azo dye coupling agent, analytical reagent
Salicylic Acid is a single organic molecule of defined composition. Salicylic Acid is therefore identified by an exact chemical formula and molecular weight.
CAS No 69-72-7 and EC No 200-712-3 are listed for Salicylic Acid in various official sources, including ECHA. Salts such as sodium salicylate (CAS No 54-21-7) and ester derivatives have separate CAS numbers.
The most important impurities of Salicylic Acid, also defined in the European Pharmacopoeia, are phenol, 4-hydroxybenzoic acid and 4-hydroxyisophthalic acid. These impurities originate from the Kolbe-Schmitt production process.
Salicylic Acid products with the same CAS number may therefore differ from one another in impurity limits and quality standard.
CHEMICAL STRUCTURE AND MOLECULAR PROPERTIES OF SALICYLIC ACID
Salicylic Acid carries a carboxyl group (–COOH) and a hydroxyl group (–OH) in adjacent (ortho) positions on a benzene ring. The SMILES notation of Salicylic Acid is C1=CC=C(C(=C1)C(=O)O)O and its InChIKey is YGSDEFSMJLZEOE-UHFFFAOYSA-N.
The Salicylic Acid molecule has 2 hydrogen bond donors, 3 hydrogen bond acceptors and 1 rotatable bond. Its topological polar surface area has been calculated as 57.5 Ų.
Salicylic Acid is a stronger acid than unsubstituted benzoic acid. The pKa of Salicylic Acid is about 3.0, while that of benzoic acid is around 4.2. This difference arises because the hydroxyl group in the ortho position facilitates dissociation of the carboxyl group.
A pKa of about 3.0 means that roughly half of Salicylic Acid is ionized at pH 3.0. This directly affects the choice of pH in formulations containing Salicylic Acid.
The octanol/water partition coefficient of Salicylic Acid has been reported as log Pow 2.25 (25 °C). This value shows that Salicylic Acid has a distinctly lipophilic character.
Its lipophilic structure allows Salicylic Acid to penetrate pores filled with sebum. This is the most important property distinguishing Salicylic Acid from water-soluble alpha hydroxy acids (AHAs).
The chemical reactivity of Salicylic Acid comes from both the carboxyl group and the phenolic hydroxyl group. Esterification of the phenolic hydroxyl group with acetic anhydride or acetyl chloride gives aspirin.
Esterification of the carboxyl group with alcohols forms salicylate esters such as methyl salicylate. Reaction of Salicylic Acid with bases gives salts such as sodium, potassium and magnesium salicylate.
PHYSICAL AND CHEMICAL PROPERTIES OF SALICYLIC ACID
Salicylic Acid is generally a white, odourless solid occurring as crystalline powder or fine needle-shaped crystals. Some sources also describe a colour ranging from white to pale yellow and a faint nutty odour.
The physical appearance of Salicylic Acid may vary depending on crystallization conditions, degree of purity and storage conditions.
General technical properties:
Physical appearance: White crystalline powder or needle-shaped crystals
Odour: Odourless
Molecular formula: C7H6O3
Molecular weight: 138.12 g/mol
CAS No: 69-72-7
EC / EINECS No: 200-712-3
Melting point: 158–161 °C
Boiling point: 211 °C (20 mmHg)
Flash point: 157 °C (closed cup)
Density: 1.44 g/cm³ (20 °C)
Refractive index: 1.565
pH: 2.4 (20 °C, saturated aqueous solution)
pKa: About 3.0
Vapour pressure: 1 hPa (114 °C)
Lower explosion limit: 1.1% (V) (200 °C)
Partition coefficient (log Pow): 2.25 (25 °C)
Solubility in water: 1.24 g/L (0 °C); 2.48 g/L (25 °C); 4.14 g/L (40 °C); 17.41 g/L (75 °C); 77.79 g/L (100 °C)
Solubility in organic solvents: 34.87% by weight in absolute ethanol (21 °C), 27.36% in propanol (21 °C), 62.48 g/100 g in methanol (21 °C), 39.6 g/100 g in acetone (23 °C), 2.22 g/100 mL in chloroform (25 °C), 2.43 g/100 g in olive oil (23 °C)
Stability: Stable under normal conditions; light-sensitive
Materials to avoid: Oxidizing agents, strong bases, iodine, fluorine, iron salts, lead acetate
Salicylic Acid is sparingly soluble in cold water but considerably more soluble in boiling water. The water solubility of Salicylic Acid is 2.48 g/L at 25 °C and reaches 77.79 g/L at 100 °C.
Its water solubility can be increased with trisodium phosphate, alkali acetates or alkali citrates. However, since Salicylic Acid may be partly converted into a salicylate salt with these salts, this should be assessed separately for efficacy in cosmetic formulations.
Salicylic Acid dissolves readily in polar organic solvents such as ethanol, acetone, methanol and propanol. This property is the main factor determining solvent choice in toner, gel and solution formulations containing Salicylic Acid.
The solubility of Salicylic Acid in olive oil of 2.43 g/100 g shows that it can also be dissolved at certain levels in oil-based systems.
Salicylic Acid is light-sensitive and can cause discolouration with iron salts. Packaging choice and raw material purity are therefore important in products containing Salicylic Acid.
The values given above are general information compiled from the literature and safety data sheets and are not binding specifications. The exact values of the Salicylic Acid product to be used should be checked against the TDS and COA documents.
HOW DOES SALICYLIC ACID WORK AT THE MOLECULAR LEVEL?
The main effect of Salicylic Acid on the skin is its keratolytic effect. Salicylic Acid most likely increases the water content of the stratum corneum by lowering the pH of the environment. As a result, the horny layer of the skin swells, softens and sheds.
At low concentrations Salicylic Acid is reported to have a keratoplastic effect, i.e. it corrects abnormal keratinization. At concentrations of about 1% and above, depending on the vehicle, a pronounced keratolytic, i.e. peeling, effect appears.
Dead skin cells (corneocytes) are bound to one another by protein bridges called desmosomes. Salicylic Acid weakens these connections between corneocytes and reduces cell cohesion. Dead cells with reduced cohesion are shed more easily from the skin surface.
Thanks to this effect, Salicylic Acid is used in products for conditions associated with excessive keratin build-up, such as acne, psoriasis, seborrhoeic dermatitis, corns, warts, keratosis pilaris and ichthyosis.
Unlike alpha hydroxy acids, Salicylic Acid has an oil-soluble structure. Thanks to this lipophilic character, Salicylic Acid can pass through the sebum barrier and penetrate into the pores.
By helping to dissolve the mixture of sebum and dead cells accumulated in the pore, Salicylic Acid contributes to reducing comedone (blackhead and whitehead) formation.
Salicylic Acid directly and reversibly inhibits the cyclooxygenase enzymes (COX-1 and COX-2), reducing the conversion of arachidonic acid into prostaglandin and thromboxane precursors. The anti-inflammatory effect of Salicylic Acid is based on this mechanism.
This effect explains why products containing Salicylic Acid can also help soothe acne-related redness and inflammation.
Salicylic Acid also has bacteriostatic and fungicidal properties. Because of these properties, Salicylic Acid can also be used as a preservative in cosmetic products.
Main functions of Salicylic Acid:
Keratolytic and exfoliating effect
Reducing comedone formation by penetrating into the pores
Reducing the formation of dandruff flakes
Anti-inflammatory effect
Bacteriostatic and fungicidal effect
Preservative effect in cosmetic products
The efficacy of Salicylic Acid depends directly on formulation pH. Since the pKa of Salicylic Acid is about 3.0, products are generally recommended to be formulated below pH 4.0 to preserve the active, non-ionized acid form.
IN WHICH INDUSTRIES IS SALICYLIC ACID USED?
Salicylic Acid has a wide range of uses, from cosmetic and dermocosmetic products to pharmaceutical synthesis, resin production and the rubber and dye industries.
According to the industrial literature, the use distribution of Salicylic Acid is approximately as follows: 55% acetylsalicylic acid (aspirin) production, 18% salicylate esters and salts, 10% resins, 10% dyes and colourants.
Main fields of use:
Cosmetic and personal care products
Dermocosmetic and dermatological products
Pharmaceutical industry
Chemical synthesis and intermediate production
Phenolic and foundry resins
Rubber industry
Dye and colourant production
Agrochemicals
Plastic product and plastic raw material manufacturing
Paint and coating manufacturing
Primary metal manufacturing
Analytical chemistry and laboratory applications
What the cosmetic and dermocosmetic industries expect from Salicylic Acid is high purity, low impurity and heavy metal content, regulatory compliance and appropriate documentation.
In the pharmaceutical industry, Salicylic Acid is expected to meet the relevant pharmacopoeia requirements. In chemical synthesis, resin and rubber applications, purity, consistent crystal structure and a technical grade suited to the process come to the fore.
COSMETIC AND DERMOCOSMETIC APPLICATIONS OF SALICYLIC ACID
The best-known field of use of Salicylic Acid is cosmetic and dermocosmetic products. Salicylic Acid is one of the key ingredients in products addressing problems associated with excessive keratin build-up and clogged pores, such as acne, blackheads, dandruff, corns and warts.
In the EU cosmetic ingredient inventory, the functions of Salicylic Acid are defined as keratolytic and preservative. The literature also reports that Salicylic Acid is used as an anti-dandruff agent, deodorant, denaturant, skin conditioning and hair conditioning agent.
Acne products:
Salicylic Acid penetrates into the pores, dissolves the build-up of sebum and dead cells and helps reduce comedone formation. Salicylic Acid is therefore used in facial cleansers, toners, gels, serums, masks and cleansing pads.
In acne products, Salicylic Acid is generally used in the range of 0.5–2%. This range is also consistent with the 2% upper limit defined in EU cosmetics legislation for non-preservative use.
Dandruff and scalp care products:
Salicylic Acid is used in anti-dandruff shampoos to reduce the formation of dandruff flakes on the scalp. In shampoos containing Salicylic Acid, the concentration is generally in the range of 2–3%.
EU cosmetics legislation allows a maximum of 3.0% Salicylic Acid in rinse-off hair products for non-preservative use.
Peeling and exfoliation products:
The peeling effect of Salicylic Acid helps improve the appearance of dull and uneven skin tone by reducing the build-up of dead cells on the skin surface. Salicylic Acid is therefore evaluated in chemical peeling and exfoliating products.
High-concentration Salicylic Acid peels (such as 30%) are generally used in dermatology clinics and professional applications.
Corn, wart and foot care products:
Because it softens and separates thickened skin, Salicylic Acid is used in products intended to remove corns and warts. In these products Salicylic Acid may be present at about 17% in flexible collodion or at levels of up to 40% in plaster and pad form.
These high-concentration Salicylic Acid products are considered medicinal products, not cosmetics.
Use as a preservative:
The bacteriostatic and fungicidal properties of Salicylic Acid allow it to be used as a preservative in cosmetic products. According to EU cosmetics legislation, Salicylic Acid may be used as a preservative at a maximum of 0.5% (as acid) in the ready-for-use product.
Concentrations of Salicylic Acid in cosmetic formulations are reported to range from 0.0008% to 3%. The Cosmetic Ingredient Review (CIR) panel concluded that Salicylic Acid is safe when formulated to avoid skin irritation and when formulated so as not to increase the skin's sensitivity to the sun.
Products containing Salicylic Acid can cause hyperpigmentation, especially in darker skin types and when a broad-spectrum sunscreen is not used. A sun protection recommendation is therefore important in products containing Salicylic Acid.
USE OF SALICYLIC ACID IN PHARMACEUTICALS AND AS A CHEMICAL SYNTHESIS INTERMEDIATE
In terms of production volume, the largest field of use of Salicylic Acid is the production of acetylsalicylic acid (aspirin). Aspirin is prepared by esterification of the phenolic hydroxyl group of Salicylic Acid with acetic anhydride or acetyl chloride.
According to the literature, about 60% of the Salicylic Acid produced in the USA in the late 1980s and early 1990s was consumed in aspirin production.
Salicylic Acid is used as a starting material in the production of salicylate esters and salts. The main derivatives obtained from Salicylic Acid are:
Acetylsalicylic acid (aspirin): Analgesic, antipyretic and anti-inflammatory active substance
Methyl salicylate: Ester used in topical products for joint and muscle pain
Sodium salicylate: Salt used as an anti-inflammatory, analgesic and antipyretic
Bismuth subsalicylate: Bismuth salt used in products for stomach complaints
Choline salicylate: Salt used topically to relieve the pain of mouth ulcers
Benzyl salicylate and isoamyl salicylate: Fragrance components
Salicylic Acid also serves as a starting material for the production of other pharmaceutical products via its ester, amide and salt derivatives.
Salicylic Acid is itself a topical active pharmaceutical ingredient. Salicylic Acid is included in the World Health Organization Model List of Essential Medicines as a 5% topical solution for seborrhoeic dermatitis, psoriasis and ichthyosis.
Salicylic Acid is described in the European, British, United States and Japanese pharmacopoeias. In the WHO ATC system, Salicylic Acid is classified under code D01AE12 among topical antifungals and under code S01BC08 among ophthalmological non-steroidal anti-inflammatories.
In pharmaceutical applications, topical Salicylic Acid products may be found in the form of lotions, creams, gels, ointments, shampoos, solutions, collodions, plasters and pads. The Salicylic Acid content in these products varies between 0.5% and 40% depending on the intended use.
Salicylic Acid to be used in pharmaceutical and synthesis applications must meet the relevant pharmacopoeia requirements, and its impurity profile must be verified with a COA.
IS SALICYLIC ACID USED IN COSMETIC, FOOD AND PHARMACEUTICAL APPLICATIONS?
Cosmetics:
Salicylic Acid is a restricted ingredient under the EU Cosmetics Regulation (EC) No 1223/2009. Salicylic Acid is regulated in entry 98 of Annex III for non-preservative use and in entry 3 of Annex V for use as a preservative.
Limits for Salicylic Acid in the ready-for-use product under Annex III (non-preservative use):
Rinse-off hair products: Maximum 3.0%
Body lotion, eye shadow, mascara, eyeliner, lipstick and roll-on deodorant: Maximum 0.5%
Other products: Maximum 2.0%
Additional conditions under Annex III:
Not to be used in products for children under 3 years of age
Not to be used in oral products
Not to be used in applications that may lead to exposure of the end user's lungs by inhalation
The purpose other than preservation must be apparent from the presentation of the product
The label of products that might be used on children under 3 must carry the warning "Not to be used for children under 3 years of age"
Under Annex V (use as a preservative), Salicylic Acid and calcium, magnesium, MEA, sodium, potassium and TEA salicylate may be used at a maximum of 0.5% (as acid) in the ready-for-use product. For this use, products for children under 3 (except shampoos), oral products and applications that may lead to exposure of the lungs by inhalation are also excluded.
The 3.0% and 2.0% limits in Annex III were introduced by Regulation (EU) 2019/1966, while the 0.5% limit for products such as body lotion and eye and lip make-up was added by Regulation (EU) 2021/850.
Under the CLP Regulation, Salicylic Acid is classified as toxic to reproduction Category 2 (H361d). In its final opinion published in 2023, the EU scientific committee SCCS concluded that the use of Salicylic Acid as a preservative at 0.5% is safe within the existing restrictions.
For cosmetic products in Türkiye, the current annexes of the Turkish Cosmetics Regulation should be taken as the basis. For products containing Salicylic Acid, it is recommended that the applicable limits be checked against the current regulatory text during product development.
Food:
Salicylic Acid is not among the permitted additives in the Turkish Food Codex Regulation on Food Additives. The use of Salicylic Acid as a preservative in foods is therefore prohibited.
Salicylic Acid was used as a food preservative in the past. However, in 1961 the Joint FAO/WHO Expert Committee on Food Additives (JECFA) did not allocate an acceptable daily intake (ADI) for Salicylic Acid and stated that it is unsuitable as a food additive.
In its 2001 evaluation, JECFA concluded that Salicylic Acid used as a flavouring agent raises no safety concern at current levels of intake. Salicylic Acid is included in the EU list of flavouring substances (Regulation (EU) No 872/2012).
In the USA, the FDA lists Salicylic Acid as a flavouring agent or adjuvant. Salicylic Acid is also among the substances in food-contact materials under 21 CFR 175.105, 175.300 and 177.2600.
Adding Salicylic Acid, under the name "domates ilacı" ("tomato medicine"), to homemade tomato paste, canned tomatoes and pickles is a serious food safety risk. The Chamber of Food Engineers of Türkiye (TMMOB Gıda Mühendisleri Odası) warns that the use of Salicylic Acid in foods is not approved and poses a health risk.
Salicylates naturally present in tomatoes, peppers, cucumbers and some fruits are not within the scope of this prohibition. The prohibition covers the addition of Salicylic Acid to foods from outside.
Pharmaceuticals:
Salicylic Acid is used in topical medicines as a keratolytic, antifungal and anti-inflammatory active ingredient. Salicylic Acid is included in the World Health Organization Model List of Essential Medicines and is described in the European, British, United States and Japanese pharmacopoeias.
In the USA, Salicylic Acid is recognized as an active ingredient in over-the-counter topical acne products at concentrations of 0.5–2%. Salicylic Acid to be used in pharmaceutical applications must comply with the relevant pharmacopoeia monograph.
INDUSTRIAL APPLICATIONS OF SALICYLIC ACID
Apart from cosmetics and pharmaceuticals, Salicylic Acid is used in various industrial applications. Technical grade Salicylic Acid is evaluated as an intermediate, particularly in agrochemicals, dyes and colourants, the rubber industry and phenolic resin production.
Resin production:
Salicylic Acid is used in the production of phenolic resins and foundry resins. According to the industrial literature, about 10% of Salicylic Acid is consumed in resin applications.
Plastic raw material and resin manufacturing and paint and coating manufacturing are among the industrial sectors in which Salicylic Acid is processed.
Rubber industry:
Salicylic Acid is used in the rubber industry as a prevulcanization retarder. In this application, Salicylic Acid helps prevent premature vulcanization of the rubber compound during processing.
Dyes and colourants:
Salicylic Acid is used as a coupling component in the production of azo dyes. According to the literature, about 10% of Salicylic Acid is directed to dye and colourant applications.
Agrochemicals:
Technical grade Salicylic Acid is used as an intermediate in the production of agrochemicals. Salicylic Acid was also used as a fungicide in the past.
Analytical chemistry:
Salicylic Acid is used in laboratories as an analytical reagent. ACS reagent grade Salicylic Acid is preferred for analytical applications.
Other industrial uses:
Chemical data reports of the US Environmental Protection Agency (EPA) state that Salicylic Acid is used in insulating materials, as a polymerization promoter, as a processing aid and as an intermediate. Primary metal manufacturing is also listed among the sectors in which Salicylic Acid is used.
The grade, purity and impurity profile of Salicylic Acid to be used in industrial applications should be determined according to the requirements of the process.
WHICH PROBLEMS CAN SALICYLIC ACID HELP SOLVE?
Clogged pores and acne:
Thanks to its oil-soluble structure, Salicylic Acid penetrates into the pores and helps dissolve the build-up of sebum and dead cells. In this way Salicylic Acid contributes to reducing the formation of blackheads and whiteheads.
Dead cell build-up and uneven skin texture:
Salicylic Acid makes it easier for dead cells to shed by weakening the bonds between corneocytes. Products containing Salicylic Acid can help improve a dull and rough-looking skin.
Dandruff:
Salicylic Acid is used in anti-dandruff shampoos because it helps reduce the formation of dandruff flakes on the scalp.
Corns and warts:
Salicylic Acid is effective in corn and wart removal products by softening and separating the thickened skin layer.
Skin conditions associated with excessive keratin build-up:
Salicylic Acid is used in dermatological products for conditions such as psoriasis, seborrhoeic dermatitis, ichthyosis, keratosis pilaris and acanthosis nigricans.
Acne-related redness and inflammation:
The anti-inflammatory effect of Salicylic Acid, based on its inhibition of COX enzymes, can help soothe acne-related redness and inflammation.
Microbial spoilage in cosmetic products:
Thanks to its bacteriostatic and fungicidal properties, Salicylic Acid can contribute to preventing microbial spoilage as a preservative in cosmetic products.
Premature vulcanization in rubber processing:
As a prevulcanization retarder, Salicylic Acid helps prevent rubber compounds from vulcanizing prematurely during processing.
Need for a starting material in synthetic chemistry:
Salicylic Acid is used as a basic starting material in the production of aspirin, salicylate esters, salicylate salts and azo dyes.
POINTS TO CONSIDER WHEN USING SALICYLIC ACID
pH and efficacy:
Since the pKa of Salicylic Acid is about 3.0, the efficacy of Salicylic Acid depends directly on formulation pH. To preserve the active acid form, products are generally recommended to be formulated below pH 4.0, preferably in the pH 3–4 range.
Rinse-off cleansers containing Salicylic Acid generally have a higher pH and a short contact time with the skin. In these products the peeling effect of Salicylic Acid may be more limited than in leave-on products.
Solubility:
Because Salicylic Acid is sparingly soluble in water, in aqueous formulations Salicylic Acid may first need to be dissolved in a suitable solvent such as ethanol or propanol. If the solvent level is insufficient, Salicylic Acid may crystallize and precipitate in the water phase.
Formulation compatibility:
Salicylic Acid is incompatible with soap-based emulsions, for example classic vanishing creams. In low-pH facial cleansers containing Salicylic Acid, surfactants such as alpha olefin sulfonates are preferred over alkyl ether sulfates (for example sodium laureth sulfate), which are prone to degradation at low pH.
Salicylic Acid is incompatible with iron salts, lead acetate, iodine, strong bases and oxidizing agents. Iron contamination can cause discolouration in products containing Salicylic Acid.
Regulatory limits:
In cosmetic products containing Salicylic Acid, the limits of 0.5%, 2.0% and 3.0% depending on product type, and the 0.5% limit for preservative use, must be observed. Salicylic Acid must not be used in products for children under 3, in oral products or in spray applications that may lead to lung exposure by inhalation.
Sun sensitivity and hyperpigmentation:
Products containing Salicylic Acid can cause hyperpigmentation, especially in darker skin types and when sunscreen is not used. It is important for products containing Salicylic Acid to include a sun protection recommendation.
Application of high concentrations to large areas:
Salicylic Acid is rapidly absorbed through intact skin. Applying high concentrations of Salicylic Acid to a large part of the body surface can raise blood salicylate levels to dangerous levels; haemodialysis may be required in such cases.
Absorption of Salicylic Acid through damaged skin is reported to be markedly higher than through intact skin. High-concentration Salicylic Acid products should therefore be used with care on damaged or large skin areas.
Reproductive toxicity:
Salicylic Acid is classified as toxic to reproduction Category 2 because it is suspected of damaging the unborn child (H361d). Special instructions should be read before working with Salicylic Acid.
Eye damage and dust:
Salicylic Acid can cause serious eye damage. Salicylic Acid dust can irritate the nose and throat; dust formation should be avoided and suitable eye protection used.
Use in foods:
Salicylic Acid must not be used as a preservative in foods. Adding Salicylic Acid to tomato paste, canned foods and pickles under the name "domates ilacı" is not legal and poses a health risk.
STARTING FORMULATION APPROACHES FOR SALICYLIC ACID
The following examples are starting approaches prepared to show how Salicylic Acid can be evaluated in the formulation development process. They are not validated commercial formulas.
The ratios given are example starting levels for preliminary laboratory trials. Since the grade of Salicylic Acid used, the other raw materials and the target product type can significantly change the results, final ratios should be determined through stability, efficacy, safety and regulatory assessments.
EXAMPLE 1: EVALUATION OF SALICYLIC ACID LEVEL AND PH IN A LEAVE-ON ACNE TONER
Objective: To determine the effect of the Salicylic Acid level and product pH on solubility, clarity and stability in a leave-on facial toner.
Starting approach:
Salicylic Acid: 0.5%, 1.0%, 1.5% and 2.0% (upper limit for non-preservative use in facial products: 2.0%)
Solvent phase (e.g. ethanol): Enough to dissolve the Salicylic Acid completely; since solubility in ethanol is about 34.87% by weight, theoretically at least about 2 parts of ethanol for every 1 part of Salicylic Acid
Water phase: To balance
Target pH: 3.0–4.0
Application approach:
Salicylic Acid is first dissolved completely in the solvent phase.
The Salicylic Acid solution is added slowly to the water phase under stirring.
The product pH is measured for each level and kept within the target range.
Samples are stored at room temperature and at low temperature and observed for Salicylic Acid crystallization, cloudiness and discolouration.
For levels where precipitation is observed, the trial is repeated with an increased solvent level.
EXAMPLE 2: SALICYLIC ACID LEVEL SCREENING IN AN ANTI-DANDRUFF SHAMPOO
Objective: To evaluate the effect of the Salicylic Acid level on product appearance, viscosity, pH and stability in an anti-dandruff shampoo.
Starting approach:
Salicylic Acid: 1.0%, 2.0% and 3.0% (upper limit for non-preservative use in rinse-off hair products: 3.0%)
Anionic surfactant: A type resistant to low pH (e.g. alpha olefin sulfonate); kept constant
Co-surfactant and thickener: Kept constant
Solvent or solubilizer: As much as needed to dissolve the Salicylic Acid
Target pH: As low as possible for the efficacy of Salicylic Acid and compatible with the surfactant system
Application approach:
Salicylic Acid is dissolved in advance in the solvent or dispersed in the surfactant phase.
Salicylic Acid is added under stirring after the surfactant system has been prepared.
Viscosity, pH, clarity and foam character are measured for each level.
Salicylic Acid precipitation, phase separation and discolouration are monitored in accelerated stability tests.
It is ensured that the anti-dandruff purpose is clearly stated in the product presentation and that the under-3 warning is included.
EXAMPLE 3: EVALUATION OF SALICYLIC ACID IN A LOW-PH FACIAL CLEANSING GEL
Objective: To compare the effect of the Salicylic Acid level and surfactant choice on product stability and performance in a rinse-off facial cleansing gel.
Starting approach:
Salicylic Acid: 0.5%, 1.0% and 2.0%
Surfactant system A: Based on alpha olefin sulfonate
Surfactant system B: Based on alkyl ether sulfate, for comparison
Solvent phase: Enough to dissolve the Salicylic Acid
Target pH: Around 3.5–4.0
Application approach:
Salicylic Acid is dissolved in the solvent phase and added to the prepared surfactant systems.
The two surfactant systems are compared at the same Salicylic Acid level.
pH, viscosity and appearance of the samples are measured at the start and after storage.
Viscosity loss or odour change due to degradation of the surfactant at low pH is observed.
As the Salicylic Acid level increases, tolerability is assessed separately by suitable methods.
PRODUCTS SIMILAR TO SALICYLIC ACID AND ALTERNATIVES
When choosing an alternative to Salicylic Acid, the target effect, solubility, depth of skin penetration, irritation potential and regulatory status should be evaluated together. Some alternatives are derivatives of Salicylic Acid, while others are ingredients with a different mechanism of action.
SALICYLIC ACID AND BETAINE SALICYLATE
Betaine salicylate is a salicylate derivative prepared with betaine of sugar beet origin and is used as an exfoliant alternative to Salicylic Acid. It is reported to be preferred especially where the use of Salicylic Acid is restricted.
According to manufacturer data, betaine salicylate shows a similar effect at about twice the concentration of Salicylic Acid; that is, about 4% betaine salicylate corresponds to a product containing 2% Salicylic Acid. There are no independent studies confirming this equivalence.
Like Salicylic Acid, the efficacy of betaine salicylate depends on pH, and a pH range of 3.8–4.2 is recommended.
SALICYLIC ACID AND CAPRYLOYL SALICYLIC ACID
Capryloyl salicylic acid, also known as lipohydroxy acid (LHA), is a fatty acid derivative of Salicylic Acid. Like Salicylic Acid, it has an oil-soluble structure.
As a larger molecule, capryloyl salicylic acid penetrates the skin more slowly and remains largely in the stratum corneum. In vitro studies have reported that Salicylic Acid penetrates the skin up to 58% further.
Capryloyl salicylic acid is generally used at a maximum of 1%. There are no studies showing that it is superior to Salicylic Acid in anti-blemish efficacy.
SALICYLIC ACID AND SALICYLATE SALTS
Sodium, potassium, calcium, magnesium, MEA and TEA salicylate are salt forms of Salicylic Acid. These salts are more soluble in water than Salicylic Acid.
According to Annex V of the EU Cosmetics Regulation, these salts may also be used together with Salicylic Acid as preservatives, at a maximum of 0.5% (as acid) in the ready-for-use product.
However, since the carboxyl group is ionized in the salt form, the keratolytic effect should not be expected to be as strong as that of Salicylic Acid in its acid form.
SALICYLIC ACID AND METHYL SALICYLATE
Methyl salicylate is the methyl ester of Salicylic Acid and is also known as oil of wintergreen. It is used in topical products for muscle and joint pain, in oral care products and as a fragrance component.
Methyl salicylate is regulated as a separate entry in Annex III of the EU Cosmetics Regulation. It has limits ranging from 0.002% (eye make-up) to 2.52% (toothpaste) depending on product type and must not be used in products for children under 6, except toothpaste.
Like Salicylic Acid, methyl salicylate is classified as toxic to reproduction Category 2.
SALICYLIC ACID AND GLYCOLIC ACID
Glycolic acid is a water-soluble alpha hydroxy acid (AHA) and is used in exfoliating products as an alternative or complement to Salicylic Acid.
Glycolic acid acts on the skin surface. Oil-soluble Salicylic Acid, on the other hand, stands out for oily and acne-prone skin because it can penetrate into the pores.
SALICYLIC ACID AND BENZOYL PEROXIDE
Benzoyl peroxide is an active substance mentioned as an alternative to Salicylic Acid in acne treatment. However, under Annex III of the EU Cosmetics Regulation, benzoyl peroxide may only be used in artificial nail systems for professional use, at a maximum of 0.7%.
For this reason, benzoyl peroxide is not an alternative to Salicylic Acid as a cosmetic ingredient in acne products in the EU; its use in acne treatment falls within the scope of medicinal products.
Other related compounds:
Other compounds structurally related to Salicylic Acid include 2,5-dihydroxybenzoic acid (gentisic acid), 2,4-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, salicylaldehyde, ethyl salicylate, propyl salicylate, butyl salicylate, isobutyl salicylate, amyl salicylate, hexyl salicylate, cis-3-hexenyl salicylate, zinc salicylate, ammonium salicylate, bismuth subsalicylate, fosfosal, 3-methylsalicylic acid, 5-methylsalicylic acid and 3,5-diiodosalicylic acid. Although these compounds belong to the same chemical family as Salicylic Acid, their fields of use differ and they should not be expected to directly replace Salicylic Acid.
QUALITY CONTROL AND PURCHASING CRITERIA FOR SALICYLIC ACID
When purchasing Salicylic Acid, deciding only on the basis of product name and price is not sufficient. Pharmaceutical, cosmetic, technical and reagent grade Salicylic Acid products differ from one another in purity, impurity limits and documentation.
Information recommended for review before purchase:
Product name and manufacturer
Quality grade (Ph. Eur., BP, USP, ACS reagent, cosmetic or technical)
Product form (crystalline powder or needle crystals)
CAS number
EC / EINECS number
Purity (assay)
Melting point
Chloride and sulphate content
Heavy metal and iron content
Related substances (4-hydroxybenzoic acid, 4-hydroxyisophthalic acid, phenol)
Sulphated ash
Loss on drying
Residual solvents
Shelf life or retest period
Typical specification parameters for Ph. Eur. / BP / USP grade Salicylic Acid:
Assay (calculated on the dried substance): 99.5–100.5%
Identity: Passes test
Appearance of solution: Passes test
Chloride (Cl): ≤ 0.01%
Sulphate (SO₄): ≤ 0.02%
Heavy metals (as Pb): ≤ 0.002%
4-Hydroxybenzoic acid: ≤ 0.1%
4-Hydroxyisophthalic acid: ≤ 0.05%
Phenol: ≤ 0.02%
Other impurities: ≤ 0.05%
Total impurities: ≤ 0.2%
Residual solvents: Passes test
Sulphated ash: ≤ 0.01%
Loss on drying: ≤ 0.5%
Typical specification parameters for ACS reagent grade Salicylic Acid:
Appearance: White powder or crystals
Purity (HPLC): ≥ 99.0%
Melting point: 158.0–161.0 °C
Residue on ignition (ash): ≤ 0.01%
Chloride: ≤ 0.001%
Substances darkened by sulphuric acid: Passes test
Iron (Fe): ≤ 2 ppm
Heavy metals (as Pb): ≤ 5 ppm
Sulphate (SO₄): ≤ 0.003%
Recommended retest period: 4 years
These values are example specifications. The exact values of the Salicylic Acid product to be used should be checked against the manufacturer's TDS and COA documents.
Difference between TDS, SDS and COA:
The TDS (Technical Data Sheet) defines the general technical properties, quality grade and typical values of Salicylic Acid. The SDS (Safety Data Sheet) contains information on the hazards of Salicylic Acid and on its safe handling, storage, transport and disposal.
The COA (Certificate of Analysis) shows the actual results of the analyses carried out on a specific batch of Salicylic Acid. The COA of every purchased batch should be checked by comparing it with the specification.
STORAGE AND TRANSPORT OF SALICYLIC ACID
Salicylic Acid should be stored in tightly closed packaging in a dry place. Since Salicylic Acid is light-sensitive, protection from direct light is recommended.
Salicylic Acid should be kept away from oxidizing agents, strong bases, iodine, fluorine, iron salts and lead acetate. Salicylic Acid falls under class 11 (combustible solids) of the German storage classification.
Salicylic Acid dust is combustible; a lower explosion limit of 1.1% (V) has been reported for the dust. Dust accumulation and ignition sources must therefore be avoided in areas where Salicylic Acid is stored and handled.
The recommended retest period is stated as 4 years for an example ACS reagent grade. The shelf life and storage conditions of the Salicylic Acid product to be used should be checked against the manufacturer's TDS.
Salicylic Acid is not regulated as a dangerous good under ADR (road), IMDG (sea) and IATA (air) rules.
SALICYLIC ACID SAFETY INFORMATION
Salicylic Acid is classified as follows under the CLP Regulation (EC) No 1272/2008:
Acute toxicity (oral), Category 4 – H302: Harmful if swallowed
Serious eye damage, Category 1 – H318: Causes serious eye damage
Reproductive toxicity, Category 2 – H361d: Suspected of damaging the unborn child
Signal word: Danger
Main precautionary statements: P201 Obtain special instructions before use; P202 Do not handle until all safety precautions have been read and understood; P264 Wash skin thoroughly after handling; P280 Wear protective gloves/protective clothing/eye protection/face protection.
Toxicological data: For Salicylic Acid, the oral LD50 (rat, male) is reported as 891 mg/kg and the dermal LD50 (rat) as > 2,000 mg/kg. Inhalation of Salicylic Acid dust can irritate the nose and throat; swallowing large amounts can cause vomiting.
When working with Salicylic Acid, dust formation should be avoided, adequate ventilation provided, and suitable protective gloves and eye and face protection used. Salicylic Acid must not be allowed to enter the drains.
Salicylic Acid waste should be disposed of in accordance with Directive 2008/98/EC, the Turkish Waste Management Regulation and other national and local regulations. Salicylic Acid is not on the REACH Candidate List of Substances of Very High Concern (SVHC).
For detailed safety, first aid, firefighting and accidental release information, the current SDS of the Salicylic Acid product to be used should be taken as the basis.
WHAT SHOULD BE CONSIDERED WHEN PURCHASING SALICYLIC ACID?
When purchasing Salicylic Acid, the quality grade of the product should first be clarified. Pharmacopoeia grade should be evaluated for cosmetic and pharmaceutical applications, reagent grade for analytical work, and technical grade Salicylic Acid for industrial applications.
The purity and impurity profile of Salicylic Acid, especially the limits for phenol, 4-hydroxybenzoic acid and 4-hydroxyisophthalic acid, should be checked on the COA.
For Salicylic Acid to be used in cosmetic and pharmaceutical applications, the limits for heavy metals, iron, chloride and sulphate should also be evaluated. Iron contamination can cause discolouration in products containing Salicylic Acid.
The appearance, colour and crystal form of Salicylic Acid should be checked. Marked deviations from a white colour may be a sign of impurity or degradation in Salicylic Acid.
It is important to obtain the current TDS, SDS and batch-specific COA together with the Salicylic Acid product. For cosmetic and pharmaceutical applications, documents demonstrating compliance with the relevant pharmacopoeia should also be requested.
The type and target market of the product in which Salicylic Acid will be used determine the regulatory limits that apply. The choice of Salicylic Acid should therefore be evaluated together with the cosmetic, pharmaceutical or food-contact legislation applicable to the product type.
The shelf life or retest period of Salicylic Acid and the recommended storage conditions should be confirmed before purchase.
SUPPLY OF SALICYLIC ACID FROM ATAMAN KİMYA
Salicylic Acid is a raw material used for different technical functions such as keratolytic action, preservative action and as a synthesis intermediate in cosmetic, dermocosmetic, pharmaceutical, chemical synthesis, resin, rubber and dye applications.
You can obtain Salicylic Acid from Ataman Kimya as follows: by sharing your field of use and technical requirements, you can contact Ataman Kimya regarding product suitability, current supply status and a quotation.
The current stock status, origin, quality grade, technical properties, packaging and specifications of the product should be confirmed with Ataman Kimya before ordering.
Sharing the following information in a quotation request makes it easier to evaluate the right Salicylic Acid product:
Industry and end application
Requested quality grade (Ph. Eur., BP, USP, cosmetic, reagent or technical)
Requested minimum purity
Impurity, heavy metal and iron limits
Formulation or process information
Estimated order quantity
Requested packaging type
Requested technical documents (TDS, SDS, COA)
TDS or COA information of the current product, if available
FREQUENTLY ASKED QUESTIONS ABOUT SALICYLIC ACID
What is Salicylic Acid?
Salicylic Acid is a beta hydroxy acid with the formula C7H6O3 that has a white crystalline structure and is sparingly soluble in water and readily soluble in alcohol. Salicylic Acid is also called 2-hydroxybenzoic acid and is used especially in cosmetics, dermatological products and aspirin production.
What does the name salicylic acid mean?
The name salicylic acid comes from "salix", the Latin name of the willow tree, from which the substance was formerly obtained. Chemically, Salicylic Acid is the derivative of benzoic acid carrying a hydroxyl group in the ortho position.
What is the CAS number of Salicylic Acid?
The CAS number of Salicylic Acid is 69-72-7 and its EC number is 200-712-3.
Are Salicylic Acid and aspirin the same thing?
No. Aspirin (acetylsalicylic acid) is a derivative produced by acetylation of the phenolic hydroxyl group of Salicylic Acid. Salicylic Acid is the starting material for the production of aspirin.
Is Salicylic Acid obtained from the willow tree?
In nature, Salicylic Acid is found in white willow bark and wintergreen leaves. However, commercial Salicylic Acid is produced from phenol by the Kolbe-Schmitt synthesis.
At what level can Salicylic Acid be used in cosmetics?
According to the EU Cosmetics Regulation, Salicylic Acid may be used for non-preservative purposes at a maximum of 3.0% in rinse-off hair products, a maximum of 0.5% in body lotion, eye shadow, mascara, eyeliner, lipstick and roll-on deodorant, and a maximum of 2.0% in other products. For use as a preservative, the limit is 0.5% as acid.
Can Salicylic Acid be used in children's products?
Salicylic Acid must not be used in cosmetic products intended for children under 3 years of age. For the use of Salicylic Acid as a preservative, this restriction does not apply to shampoos.
Is Salicylic Acid soluble in water?
Salicylic Acid is sparingly soluble in cold water; its water solubility at 25 °C is 2.48 g/L. Salicylic Acid dissolves readily in ethanol, acetone, methanol and propanol.
At what pH is Salicylic Acid effective?
Since the pKa of Salicylic Acid is about 3.0, products containing Salicylic Acid are generally recommended to be formulated in the pH 3–4 range to preserve the active acid form.
Can Salicylic Acid be used in foods?
No. Salicylic Acid is not among the permitted additives in the Turkish Food Codex. Adding Salicylic Acid to tomato paste, canned foods and pickles under the name "domates ilacı" is not legal and poses a health risk.
Is Salicylic Acid a hazardous substance?
Salicylic Acid is harmful if swallowed, can cause serious eye damage and is suspected of damaging the unborn child. When working with Salicylic Acid, the protective measures stated in the SDS should be followed.
Is Salicylic Acid a dangerous good for transport?
No. Salicylic Acid is not regulated as a dangerous good under ADR, IMDG and IATA rules.
What is the difference between Salicylic Acid and betaine salicylate?
Betaine salicylate is a salicylate derivative used as an alternative to Salicylic Acid. According to manufacturer data, betaine salicylate shows a similar effect at about twice the concentration of Salicylic Acid; this equivalence has not been confirmed by independent studies.
What is the shelf life of Salicylic Acid?
The shelf life of Salicylic Acid varies by grade and manufacturer. For an example ACS reagent grade, the recommended retest period is 4 years; the shelf life of the Salicylic Acid to be used should be checked against the TDS.
SALICYLIC ACID – TECHNICAL SUMMARY
Salicylic Acid, known in Turkish as Salisilik Asit, is a beta hydroxy acid with the formula C7H6O3 that has a white crystalline structure, is sparingly soluble in water, readily soluble in alcohol and has an oil-soluble character. Also known as 2-Hydroxybenzoic Acid, o-Hydroxybenzoic Acid and Acidum Salicylicum, Salicylic Acid stands out for its keratolytic, anti-inflammatory, bacteriostatic and fungicidal properties.
Salicylic Acid is not a single commercial product type. Although pharmacopoeia (Ph. Eur., BP, USP), cosmetic, reagent and technical grade Salicylic Acid products are based on the same chemical structure, they differ in purity, impurity limits, documentation and fields of use.
CAS No 69-72-7 and EC No 200-712-3 are used for Salicylic Acid. Commercial Salicylic Acid is produced from phenol by the Kolbe-Schmitt synthesis; its main impurities are phenol, 4-hydroxybenzoic acid and 4-hydroxyisophthalic acid.
Salicylic Acid is mainly used in acne, dandruff, corn and wart products, as a cosmetic preservative, in the production of aspirin and salicylate esters and salts, in phenolic and foundry resins, as a prevulcanization retarder in the rubber industry and in azo dye production. The use of Salicylic Acid in cosmetic products is subject to limits of 0.5%, 2.0% and 3.0% depending on product type and a 0.5% limit for preservative use.
Since Salicylic Acid is harmful if swallowed, can cause serious eye damage and is classified as toxic to reproduction Category 2, appropriate occupational safety measures must be taken during handling and the current SDS must be taken as the basis. Salicylic Acid must not be used as a preservative in foods.
Companies planning to source Salicylic Acid from Ataman Kimya are advised to confirm product suitability with Ataman Kimya by sharing their field of use, requested quality grade, minimum purity, impurity limits, quantity and technical documentation needs.
