Hydroquinone: A Misunderstood Ingredient

Skin pigment disorders may not be life threatening but they can take a toll on a person’s self-esteem and self-image. There are many topical ingredients that can help with reducing the severity of pigmentation such as licorice root, kojic acid, azelaic acid, arbutin, and niacinamide but hydroquinone has been the gold standard for over 40 years. It has recently come under fire for its safety after the regulatory agencies of Japan, Europe and the U.S. began looking at over-the-counter product reports.

The concern arose when research evidence showed that benzene, a known carcinogenic, is metabolized into a hydroquinone by-product and also the possibility of developing permanent depigmentation and/or excessive hyperpigmentation called ochronosis. (JJ Nordlund, 2006). It’s important to note that benzene and hydroquinone are not the same thing. Many researchers and doctors believe there is more evidence for the safety of hydroquinone versus studies showing adverse concerns. (James Norlund, 2006)

As a chemical compound, hydroquinone can be found naturally in many foods including blueberries, pears, cranberries, broccoli, coffee beans and red wine. (Deisinger, Hill, & English, 1996) Even people who haven’t had occupational exposure to it and keep to a low hydroquinone diet can have discernible levels of it in their blood and urine. It was first discovered to affect pigment in 1936 when H. Oettel noticed graying of black-haired cats after they ingested hydroquinone daily over a period of 6-8 weeks. (Oettel, 1956) Subsequent studies throughout the years have proven the chemical’s efficacy for skin lightening.

Many of these studies have been conducted on mice and rats both in vitro (in a Petri dish or test tube) and in vivo (in the actual animal). But let’s face it, rodents aren’t humans and they react to things differently. There are some species of rats that are genetically more sensitive to hydroquinone. There just doesn’t seem to be enough substantiated data stating that hydroquinone is definitively dangerous. Depending on what camp a person supports, research either for or against its use can be found. For instance, a study by Kari published in Food and Toxicology documented growth of renal tumors in rodents who were force-fed hydroquinone. (FW Kari, September 1992) On the flip side in a different experiment done by Ames, hydroquinone was found not to be carcinogenic. (J Devillers, 1990)

Even the possible concern for developing permanent depigmentation or ochronosis from excessive topical hydroquinone use isn’t prevalent in the U.S. as it is in other countries like South Africa. One reason is that some of these overseas products had high concentrations of hydroquinone with other added active chemicals like phenol or resorcinol. (DeCaprio, 1999) Throw some sun exposure into the mix and an adverse reaction is more likely to happen. “Despite the occasional appearance of clinical case reports in the published literature, significant side effects from the use of skin preparations containing HQ are uncommon and generally associated with improper or excessive use.” (DeCaprio, 1999)

In the end, many doctors agree that there just isn’t enough evidence to prove that topical hydroquinone is a dangerous cosmetic ingredient. In over 40 years there have been no reports of topical HQ being carcinogenic. (James Norlund, 2006) All those regulatory agencies mentioned earlier have also concluded that there isn’t enough data to classify it as a carcinogen. It’s the most effective skin lightening ingredient with few side effects as long as the product is used correctly. Talk to your skin care professional about incorporating it into your routine.

DeCaprio, A. P. (1999). The Toxicology of Hydroquinone-Relevance to Occupational and Environmental Exposure. Critical Reviews in Toxicology , 283-330.
Deisinger, P. J., Hill, T. S., & English, J. C. (1996). Human Exposure to Naturally Occurring Hydroquinone. Journal of Toxicology and Environmental Health , 31-46.
FW Kari, J. B. (September 1992). Toxicity and carcinogenicity of hydroquinone in F344/N rats and B6C3F1 mice. Food and chemical toxicology : an international journal published for the British Industrial Biological Research Association , 737-747.
J Devillers, P. B. (1990). Environmental and health risks of hydroquinone. Ecotoxicology and Environmental Safety , 327-354.
James Norlund, P. G.-P. (2006). Letters to the Editor: The safety of hydroquinone. Journal Of Cosmetic Dermatology . Blackwell Publishing.
JJ Nordlund, P. G. (2006). The Safety of Hydroquinone. European Academy of Dermatology and Venereology , 781-787.
Oettel, H. (1956). Hydroquinone Poisoning. Arch Exp Pathol Pharmacol , 319-362.