Hydroquinone in Skin Care Products
Hydroquinone is a tyrosinase inhibitor used to inhibit melanin production and produce skin lightening and whitening. Hydroquinone is found in skin care products for hyperpigmentation. Hydroquinone creams and other hydroquinone products require a prescription. Is hydroquinone safe? I review hydroquinone and give you my perspective as a dermatologist.
What Is Hydroquinone Used For?
Hydroquinone is the strongest skin whitening ingredient sold in the United States. It is used to treat melasma, dark spots on the skin, hyperpigmentation, post inflammatory hyperpigmentation and any other dyschromias that are caused by an excess of melanin.
Is Hydroquinone Safe? What are the Dangers of Hydroquinone?
Hydroquinone was banned in Europe in 2000. In Asia, its use is highly regulated. Hydroquinone (HQ) was used in over the counter skin care and cosmetic products at a concentration of 2% or less without a prescription until the U.S. CARES Act was passed in 2020. Subtitle F of this act changed the way hydroquinone was regulated and hydroquinone is now considered a drug and requires a prescription.
Hydroquinone has been used for many years by dermatologists to treat pigmentation disorders, with few reports of serious side effects. The reason people worry about the danger of hydroquinone is because it is a metabolite of cancer-causing benzene. However, this does not mean that hydroquinone causes cancer.
Some studies have shown that large doses of hydroquinone taken by mouth (not topical use) resulted in some evidence of cancer in rats. However, Hydroquinone is detoxified in the liver in humans, and metabolized very differently than in rats.5,6 In humans, HQ is probably metabolized to detoxified derivatives, such as glucuronide and sulfate conjugates of HQ.7
In the 40 years HQ has been on the market for the treatment of skin hyperpigmentation and no human cases of cancer have been attributed to its use.
The main danger of hydroquinone is a condition called exogenous ochronosis.8 Ochronosis is blue-black spots on the skin that occur in the area of HQ application. This occurs after prolonged use of HQ and is more common in Asians and darker skin types.9 For this reason, the FDA decided that HQ should be used under a doctor’s supervision.
Topical HQ products are thought to cause exogenous ochronosis by inhibiting the enzyme homogentisic acid oxidase in the skin. This results in the local accumulation of homogentisic acid that then polymerizes to form ochronotic pigment.10 Despite the widespread use of HQ, only 30 cases of ochronosis have been attributed to its use in North America.6
Side Effects From Hydroquinone
It is not uncommon for hydroquinone to case an allergic skin rash. Nail discoloration may also occur.
The incidence of side effects from HQ may also be decreased through the use of lower strengths of HQ, using a test site first to determine the presence of allergy, and taking “hydroquinone holidays” every 3-4 months.
Where To Buy Hydroquinone?
Prescription drugs may contain hydroquinone (4%), and custom pharmacy formulations include hydroquinone (2% to ≥10%) as an ingredient.
How Does Hydroquinone Work to Lighten Skin?
Hydroquinone is a type of skin lightener found in skin care products known as a tyrosinase inhibitor.
Hydroquinone lightens skin several ways:
- Inhibits tyrosinase by decreasing its activity by 90%.3
- Cytotoxic to melanocytes.2
- Causes reversible inhibition of cellular metabolism by affecting both DNA and RNA synthesis.
How Is Hydroquinone Used To Lighten Dark Spots On The Skin?
Hydroquinone may be used alone, however it is often combined with skin lightening ingredients such as tretinoin, glycolic acid, kojic acid, azelaic acid, and corticosteroids.4
How Long Does it Take Hydroquinone to Work?
As with all tyrosinase inhibitors, it often takes 6 – 12 weeks before any improvement becomes noticeable.
Is Hydroquinone a natural ingredient? Where Does Hydroquinone come from?
HQ occurs naturally as an ingredient in various plant-derived food and beverage products, such as vegetables, fruits, grains, coffee, tea, beer, and wine.1
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- DeCaprio AP. The toxicology of hydroquinone—relevance to occupational and environmental exposure. Crit Rev Toxicol. 1999;29:283.
- Penney KB, Smith CJ, Allen JC. Depigmenting action of hydroquinone depends on disruption of fundamental cell processes. J Invest Dermatol. 1984;82:308.
- Nordlund JJ. Postinflammatory hyperpigmentation. Dermatol Clin. 1988;6:185.
- Guevara IL, Pandya AG. Melasma treated with hydroquinone, tretinoin and a fluorinated steroid. Int J Dermatol. 2001;40:212.
- Bates B. Derms react to possible FDA ban of hydroquinone: cite poor scientific reasoning, ethnic bias. Skin and Allergy News. 2007;38:1.
- Nordlund JJ, Grimes PE, Ortonne JP. The safety of hydroquinone. J Eur Acad Dermatol Venerol. 2006;20:781.
- Picardo M, Carrera M. New and experimental treatments of cloasma and other hypermelanoses. Dermatol Clin. 2007; 25:353.
- Lawrence N, Bligard CA, Reed R, et al. Exogenous ochronosis in the United States. J Am Acad Dermatol. 1988;18: 1207.
- Barrientos N, Oritz-Frutos J, Gómez E, et al. Allergic contact dermatitis from a bleaching cream. Am J Contact Dermat. 2001;12:33.
- Kramer KE, Lopez A, Stefanato CM, et al. Exogenous ochronosis. J Am Acad Dermatol. 2000;42:869.
- Baumann L. Depigmenting Agents in Baumann’s Cosmetic Dermatology (McGraw Hill 2022)