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CAS NUMBER: 123-31-9
EC NUMBER: 204-617-8
MOLECULAR FORMULA: C6H4-1,4-(OH)2
MOLECULAR WEIGHT: 110.11
Hydroquinone is added to a number of industrial monomers to inhibit polymerization during shipping, storage, and processing.
Hydroquinone is a light-tan, light-gray, or colorless crystal.
Exposure to hydroquinone may cause irritation to the eyes and central nervous system.
Workers may be harmed from exposure to hydroquinone.
The level of exposure depends upon the dose, duration, and work being done.
Hydroquinone is a Skin-lightening agent.
Hydroquinone bleaches the skin which is helpful in treating a different form of hyperpigmentation.
Hydroquinone bleaches the skin and decreases the number of melanocytes present.
Melanocytes make melanin that produces the skin tone.
Hydroquinone is available in the form of cream, gel, lotion and emulsion.
Hydroquinone Premium is a polymerisation inhibitor used in process, transport and storage.
Hydroquinone is designed for various applications such as: synthesis intermediate for rubber, dyes and for Agrochemicals and Pharmaceuticals industries.
Hydroquinone is a topical lightening product found in OTC products, and is used to correct skin discoloration associated with disorders of hyperpigmentation including melasma, post-inflammatory hyperpigmention, sunspots, and freckles.
Hydroquinone can be used alone, but is more frequently found in combination with other agents such as alpha-hydroxy acids, corticosteroids, retinoids, or sunscreen.
Hydroquinone is a depigmenting agent used to treat dyschromia, a condition of skin discoloration or patches of uneven skin color.
Hydroquinone is an organic compound naturally found in many plants including coffee.
Hydroquinone is produced as an inhibitor, an antioxidant, and an intermediate in the synthesis of dyes, motor fuels, and oils; in photographic processing; and naturally in certain plant species, Hydroquinone is a phenol derivative with antioxidant properties that can cause toxicity in several organs, notably the kidney.
Used as a topical treatment for skin hyperpigmentation and in various cosmetic products, it is metabolized mainly to glutathione conjugates and forms mutagenic DNA adducts in in-vitro systems.
Hydroquinone is a skin-lightening agent.
Hydroquinone bleaches the skin, which can be helpful when treating different forms of hyperpigmentation.
Historically, there’s been some back-and-forth on the safety of hydroquinone.
Hydroquinone bleaches your skin by decreasing the number of melanocytes present.
In cases of hyperpigmentation, more melanin is present due to an increase in melanocyte production.
By controlling these melanocytes, your skin will become more evenly toned over time.
Hydroquinone takes about four weeks on average for the ingredient to take effect.
Hydroquinone may take several months of consistent use before you see full results.
Hydroquinone is used to treat skin conditions related to hyperpigmentation.
Although hydroquinone can help fade red or brown spots that have lingered, Hydroquinone won’t help with active inflammation.
For example, the ingredient can help minimize acne scarring, but it won’t have an effect on redness from active breakouts.
Hydroquinone is used to lighten the dark patches of skin (also called hyperpigmentation, melasma, "liver spots," "age spots," freckles) caused by pregnancy, birth control pills, hormone medicine, or injury to the skin.
This medicine works by blocking the process in the skin that leads to discoloration.
Follow all directions on the product package, or use as directed by your doctor.
Before using, apply a small amount of this medicine to an area of unbroken skin, and check the area within 24 hours for any serious side effects.
If the test area is itching, red, puffy, or blistering, do not use this product and contact your doctor.
If there is just mild redness, then treatment with this product may begin.
Apply this medication to the affected areas of skin, usually twice daily or as directed by your doctor.
This medication is for use on the skin only.
If Hydroquinone is used incorrectly, unwanted skin lightening may occur.
Avoid getting this product in your eyes or on the inside of your nose or mouth.
If you do get this medication in those areas, flush with plenty of water.
This medication may make the treated areas of skin more sensitive to the sun.
Avoid prolonged sun exposure, tanning booths, and sunlamps. Use a sunscreen and wear protective clothing on the treated areas of skin when outdoors.
Use this medication regularly to get the most benefit from it.
To help you remember, use Hydroquinone at the same times each day.
Hydroquinone, also known as benzene-1,4-diol or quinol, is an aromatic organic compound that is a type of phenol, a derivative of benzene, having the chemical formula C6H4(OH)2.
Hydroquinone has two hydroxyl groups bonded to a benzene ring in a para position.
Hydroquinone is a white granular solid.
Substituted derivatives of Hydroquinone are also referred to as hydroquinones.
The name "hydroquinone" was coined by Friedrich Wöhler in 1843.
Hydroquinone is produced industrially by two main routes.
The most widely used route is similar to the cumene process in reaction mechanism and involves the dialkylation of benzene with propene to give 1,4-diisopropylbenzene.
Hydroquinone reacts with air to afford the bis(hydroperoxide), which is structurally similar to cumene hydroperoxide and rearranges in acid to give acetone and hydroquinone.
A second route involves hydroxylation of phenol over a catalyst.
A potentially significant synthesis of hydroquinone from acetylene and iron pentacarbonyl has been proposed.
Hydroquinone serves as a catalyst, rather than as a reagent, in the presence of free carbon monoxide gas.
Rhodium or ruthenium can substitute for iron as the catalyst with favorable chemical yields but are not typically used due to their cost of recovery from the reaction mixture.
Hydroquinone and its derivatives can also be prepared by oxidation of various phenols.
Examples include Elbs persulfate oxidation and Dakin oxidation.
Hydroquinone was first obtained in 1820 by the French chemists Pelletier and Caventou via the dry distillation of quinic acid.
The reactivity of hydroquinone's hydroxyl groups resembles that of other phenols, being weakly acidic.
The resulting conjugate base undergoes easy O-alkylation to give mono- and diethers.
Similarly, hydroquinone is highly susceptible to ring substitution by Friedel–Crafts reactions such as alkylation.
This reaction is exploited en route to popular antioxidants such as 2-tert-butyl-4-methoxyphenol (BHA).
The useful dye quinizarin is produced by diacylation of hydroquinone with phthalic anhydride.
Hydroquinone undergoes oxidation under mild conditions to give benzoquinone.
Hydroquinone can be reversed.
Some naturally occurring hydroquinone derivatives exhibit this sort of reactivity, one example being coenzyme Q.
Industrially this reaction is exploited both with hydroquinone itself but more often with its derivatives where one OH has been replaced by an amine.
When colorless hydroquinone and benzoquinone, a bright yellow solid, are cocrystallized in a 1:1 ratio, a dark-green crystalline charge-transfer complex (melting point 171 °C) called quinhydrone (C6H6O2·C6H4O2) is formed.
Hydroquinone dissolves in hot water, where the two molecules dissociate in solution.
Hydroquinones are one of the two primary reagents in the defensive glands of bombardier beetles, along with hydrogen peroxide (and perhaps other compounds, depending on the species), which collect in a reservoir.
The reservoir opens through a muscle-controlled valve onto a thick-walled reaction chamber.
This chamber is lined with cells that secrete catalases and peroxidases.
When the contents of the reservoir are forced into the reaction chamber, the catalases and peroxidases rapidly break down the hydrogen peroxide and catalyze the oxidation of the hydroquinones into p-quinones.
These reactions release free oxygen and generate enough heat to bring the mixture to the boiling point and vaporize about a fifth of it, producing a hot spray from the beetle's abdomen.
Hydroquinone derivatives are the principal irritants exuded by the poodle-dog bush, which can cause severe contact dermatitis in humans.
Hydroquinone is thought to be the active toxin in Agaricus hondensis mushrooms.
Hydroquinone has been shown to be one of the chemical constituents of the natural product propolis.
Hydroquinone is also one of the chemical compounds found in castoreum.
Hydroquinone is gathered from the beaver's castor sacs.
Hydroquinone cream is the standard depigmentation or skin lightening agent.
Hydroquinone is used to treat areas of dyschromia, such as in melasma, chloasma, solar lentigines, freckles, and post-inflammatory hyperpigmentation.
This activity outlines the indications, mechanism of action, methods of administration, important adverse effects, contraindications, and monitoring of hydroquinone, so providers can direct patient therapy to optimal outcomes in conditions where it is indicated.
Hydroquinone acts as a skin depigmentation agent by inhibiting melanin synthesis.
Hydroquinone inhibits the conversion of L-3,4- dihydroxyphenylalanine (L-DOPA) to melanin by inhibiting tyrosinase due to its structural similarity to an analog of melanin precursors
Hydroquinone is only used topically as a depigmentation agent.
A thin layer is applied with fingertips and rubbed into the face (or other affected areas) 1 to 2 times a day for 3 to 6 months.
If there are no results after 2 to 3 months, hydroquinone should be discontinued.
Hydroquinone is essential to evenly apply hydroquinone over the entire face to prevent uneven pigmentation and use concurrently with sunscreen to protect from damaging UV light, which increases pigmentation.
Physicians recommended stopping treatment after this time for a few months before restarting to decrease the risk of side effects.
Hydroquinone can also be applied during weekends only or three times a week for more extended maintenance therapy with minimal complications.
Hydroquinone is available in 2% over the counter or as 4% prescribed.
Hydroquinone comes in the following dose forms: cream, emulsion, gel, or solution.
Hydroquinone is used in a cream or lotion formulation in a concentration of 1-5%.
Hydroquinone is often found in a combination formulation with other skin lightening agents such as topical retinoids (to increase efficiency) and low potency topical steroids (to reduce irritancy).
Hydroquinone is applied topically just to the hyperpigmented skin only, twice daily for 3 months, after which time many patients maintain their improvement by using it twice each week.
If there has been no benefit after 3 months of treatment, then the hydroquinone should be stopped.
Management of the underlying cause of the hyperpigmentation is also recommended.
Hydroquinone is particularly effective for the treatment of postinflammatory hyperpigmentation which is unlikely to recur provided the underlying inflammatory dermatosis is also controlled.
Hydroquinone is a chemical that a person can use to lighten their skin tone.
Hydroquinone is available as a cream, gel, lotion, or emulsion.
Hydroquinone is generally safe to use, but some people may experience side effects, such as dry skin.
Hydroquinone is a chemical that bleaches the skin.
Hydroquinone can come as a cream, emulsion, gel, or lotion.
A person can apply Hydroquinones directly to the skin.
Creams that contain hydroquinone are available with a prescription from a doctor.
People may use hydroquinone as a form of treatment for hyperpigmentation skin conditions, wherein some areas of skin grow darker than surrounding areas.
Hydroquinone is a depigmenting agent used to lighten areas of darkened skin such as freckles, age spots, chloasma, and melisma caused by pregnancy, birth control pills, hormone medicine, or injury to the skin. Hydroquinone decreases the formation of melanin in the skin.
Melanin is the pigment in skin that gives it a brown color.
Hydroquinone (HQ) is the most commonly used tyrosinase inhibitor and is often the primary treatment option for postinflammatory hyperpigmentation and melasma.
The use of HQ results in the reversible inhibition of cellular metabolism by affecting both DNA and RNA production and reduces tyrosinase activity by 90%.
Although effective alone, HQ is often combined with other agents such as tretinoin, glycolic acid, kojic acid, and azelaic acid
Hydroquinone is a white, odorless, crystalline solid with an extremely low vapor pressure.
Hydroquinone is moderately soluble in water and highly soluble in alcohol.
Hydroquinone occurs in the environment as a result of anthropogenic processes, as well as in natural products from plants and animals.
In the soil, hydroquinone is expected to biodegrade under aerobic conditions.
Hydroquinone may be removed from the soil by oxidation processes or by direct photolysis on the surface.
Hydroquinone is a topical skin-bleaching agent used in the cosmetic treatment of hyperpigmented skin conditions.
The effect of skin lightening caused by hydroquinone is reversible when exposed to sunlight and therefore requires regular use until desired results are achieved.
Various preparations are available including creams, emulsions, gels, lotions and solutions.
Hydroquinone is available over the counter in a 2% cream and can be prescribed by your dermatologist in higher concentrations.
Hydroquinone produces reversible lightening of the skin by interfering with melanin production by the melanocytes.
Specifically, inhibition of the enzymatic conversion of tyrosine to DOPA (dihydroxyphenylalanine) results in the desired chemical reduction of pigment.
Hydroquinone causes a decrease in the number of melanocytes and decreased transfer of melanin leading to lighter skin.
Hydroquinone is frequently found in skin-lightening products like bleaching creams.
Hydroquinone works by limiting your production of melanin, the hormone that darkens your skin.
While some people use Hydroquinone to lighten their darker skin, hydroquinone creams are most commonly used to lighten small, dark patches like sunspots or hyperpigmentation.
Hydroquinone belongs to a combination of 'skin cosmetics' primarily used for brighter, more radiant skin complexation.
Hydroquinone is also used to clears the complexion and acne scars, hyperpigmentation, melasma, and photoaging (premature ageing of the skin caused by repeated exposure to UV radiation).
Hyperpigmentation is a skin condition in which patches of skin become darker in colour than the normal surrounding skin.
Melasma is a common skin problem that causes dark, discoloured patches on your skin.
Dark spots occur when some skin areas start producing more melanin (a natural pigment that gives colour to eyes, hair and skin), ranging from light to dark brown.
Hydroquinone contains Hydroquinone (skin lightening or bleaching agent) which works by decreasing the amount of melanin (a skin pigment) that is responsible for the darkening of the skin.
Hydroquinone is primarily used to treat melasma (dark brown patch on skin), hyperpigmentation.
Hydroquinone is available in topical (for skin use) gel, cream, and emulsion forms.
Hydroquinone is for external use only.
Avoid contact with eyes, eyelids, lips, mouth, and nose.
If the medicine comes in contact with any of these areas, rinse with water immediately.
Do not use Hydroquinone on sunburned, windburned, dry, or irritated skin.
Common side effects of Hydroquinone include dry skin, erythema (skin redness), burning sensation, mild itching, skin irritation.
Most of these side effects of Hydroquinone do not require medical attention and gradually resolve over time.
Hydroquinone is used as a developing agent in black-and-white photography, lithography, and x-ray films.
Hydroquinone is also used as an intermediate to produce antioxidants for rubber and food.
Hydroquinone (HQ) is produced by the oxidation of aniline or phenol, by the reduction of quinone, or from a reaction of acetylene and carbon monoxide.
Hydroquinone occurs naturally as a glucose ether, also known as arbutin, in the leaves of many plants and in fruits, as well as one of the agents used in the defense mechanism of the bombardier beetle, family Carabidae.
Hydroquinone, a colorless, hexagonal prism, has been reported to be a good antimitotic and tumor-inhibiting agent.
Hydroquinone is a reducing agent used in a photographic developer, which polymerizes in the presence of oxidizing agents.
In the manufacturing industry it may occur include bacteriostatic agent, drug, fur processing, motor fuel, paint, organic chemicals, plastics, stone coating, and styrene monomers.
Hydroquinone interferes with the production of the pigment melanin by epidermal melanocytes through at least two mechanisms: it competitively inhibits tyrosinase, one of the principal enzymes responsible for converting tyrosine to melanin, and it selectively damages melanocytes and melanosomes.
Hydroquinone was introduced in 1965 as a topical depigmenting agent for hyperpigmentation.
At high concentrations hydroquinone is corrosive and in most countries has been restricted to the level of approximately 2% and limited to the period of less than 2 months.
Hydroquinone is a slight explosion hazard when exposed to heat. Incompatible with strong oxidizing agents.
Hydroquinone reacts with oxygen and sodium hydroxide.
Hydroquinone is used in photography developers (black and white, X-ray, and microfilms), in plastics, in hair dyes as an antioxidant and hair colorant.
Hydroquinone is found in many skin bleaching creams.
USES:
Hydroquinone has a variety of uses principally associated with its action as a reducing agent that is soluble in water.
Hydroquinone is added to a number of industrial monomers to inhibit polymerization during shipping, storage, and processing.
Hydroquinone is a major component in most black and white photographic developers for film and paper where, with the compound metol, it reduces silver halides to elemental silver.
There are various other uses associated with its reducing power.
As a polymerisation inhibitor, exploiting its antioxidant properties, hydroquinone prevents polymerization of acrylic acid, methyl methacrylate, cyanoacrylate, and other monomers that are susceptible to radical-initiated polymerization.
By acting as a free radical scavenger, hydroquinone serves to prolong the shelflife of light-sensitive resins such as preceramic polymers.
Hydroquinone can lose a hydrogen cation from both hydroxyl groups to form a diphenolate ion.
The disodium diphenolate salt of hydroquinone is used as an alternating comonomer unit in the production of the polymer PEEK.
Hydroquinone is used as a topical application in skin whitening to reduce the color of skin.
Hydroquinone does not have the same predisposition to cause dermatitis as metol does.
In 2006, the United States Food and Drug Administration revoked its previous approval of hydroquinone and proposed a ban on all over-the-counter preparations.
The FDA officially banned hydroquinone in 2020 as part of a larger reform of the over-the-counter drug review process.
The FDA stated that hydroquinone cannot be ruled out as a potential carcinogen.
This conclusion was reached based on the extent of absorption in humans and the incidence of neoplasms in rats in several studies where adult rats were found to have increased rates of tumours, including thyroid follicular cell hyperplasias, anisokaryosis (variation in nuclei sizes), mononuclear cell leukemia, hepatocellular adenomas and renal tubule cell adenomas.
Numerous studies have revealed that hydroquinone, if taken orally, can cause exogenous ochronosis, a disfiguring disease in which blue-black pigments are deposited onto the skin; however, skin preparations containing the ingredient are administered topically.
The FDA had classified hydroquinone in 1982 as a safe product - generally recognized as safe and effective (GRASE), however additional studies under the National Toxicology Program (NTP) were suggested in order to determine whether there is a risk to humans from the use of hydroquinone.
NTP evaluation showed some evidence of long-term carcinogenic and genotoxic effects.
While using hydroquinone as a lightening agent can be effective with proper use, it can also cause skin sensitivity.
Using a daily sunscreen with a high PPD (persistent pigment darkening) rating reduces the risk of further damage.
Hydroquinone is sometimes combined with alpha-hydroxy acids that exfoliate the skin to quicken the lightening process.
In the United States, topical treatments usually contain up to 2% in hydroquinone.
Otherwise, higher concentrations (up to 4%) should be prescribed and used with caution.
While hydroquinone remains widely prescribed for treatment of hyperpigmentation, questions raised about its safety profile by regulatory agencies in the EU, Japan, and USA encourage the search for other agents with comparable efficacy.
Several such agents are already available or under research, including azelaic acid, kojic acid, retinoids, cysteamine, topical steroids, glycolic acid, and other substances.
One of these, 4-butylresorcinol, has been proven to be more effective at treating melanin-related skin disorders by a wide margin, as well as safe enough to be made available over the counter.
APPLICATION:
-Reducing Agents
-Organic Intermediates
-Bleaching Agents
USAGE AREAS:
-Paints & Coatings
-Agriculture
-Chemical Manufacturing
-Research Chemicals
PHYSICAL AND CHEMICAL PROPERTIES:
-Boiling point: 287 °C (1013 hPa)
-Density: 1.332 g/cm3 (15 °C)
-Flash point: 165 °C
-Ignition temperature: 515 °C
-Melting Point: 171 °C (decomposition)
-pH value: 3.7 (70 g/l, H₂O)
-Vapor pressure: 1 hPa (132 °C)
-Bulk density: 600 kg/m3
-Solubility: 70 g/l
SPECIFICATION:
-vapor density: 3.81 (vs air)
-vapor pressure: 1 mmHg ( 132 °C)
-assay: ≥99%
-autoignition temp.: 930 °F
-bp: 285 °C (lit.)
-mp: 172-175 °C (lit.)
-SMILES string: Oc1ccc(O)cc1
-InChI: 1S/C6H6O2/c7-5-1-2-6(8)4-3-5/h1-4,7-8H
-InChI key: QIGBRXMKCJKVMJ-UHFFFAOYSA-N
STORAGE:
Store at +15°C to +25°C.
SYNONYM:
123-31-9
Quinol
1,4-Dihydroxybenzene
p-Benzenediol
p-Hydroquinone
p-Hydroxyphenol
p-Dihydroxybenzene
4-Hydroxyphenol
Benzoquinol
Eldoquin
hydroquinol
Eldopaque
Phiaquin
p-Dioxybenzene
Dihydroquinone
Hydroquinole
Idrochinone
Tecquinol
Dihydroxybenzene
Solaquin forte
Benzohydroquinone
Arctuvin
Hidroquinone
Tequinol
IUPAC NAMES:
1,4-Benzenediol
1,4-Benzenediol, 1,4-Dihydroxybenzene, HQ, Quinol
1,4-Benzodiol
1,4-DIHYDROXYBENZENE
1,4-Dihydroxybenzene
1,4-dihydroxybenzene
1,4-dihydroxybenzene; hydroquinone; quinol
1,4-dyhydroxybenzene; hydroquinone, quinol
benzene, 1,4-dihydroxy
Benzene-1,4-diol
benzene-1,4-diol
TRADE NAMES:
Hydroquinone
Hydroquinone IG
Hydroquinone Photo
Hydroquinone Technical
