Benzoyl Peroxide Safety (originally by willow569)

Q: Is there a link between benzoyl peroxide and skin cancer?

Currently, no research has found a link between benzoyl peroxide use and skin cancer in humans. Two studies that investigated the link between benzoyl peroxide and skin cancer in people found no increased risk of skin cancer in people who had used benzoyl peroxide to treat acne. ^{1 2}

After conducting a series of studies and a doing a comprehensive review of the existing research on the link between benzoyl peroxide and skin cancer, one researcher concluded that aoeno epidemiological evidence exists of a carcinogenic effect of skin treatment with BPO containing gels or ointments in 5 or 10% concentrations.a ³ Other experts have concluded that topical benzoyl peroxide is considered to be a safe treatment for acne and that there is no current evidence to indicate that it poses a carcinogenic or toxicological risk to humans. ^{4 5}

Research studies have used cancer-sensitive strains of mice to study the effects of benzoyl peroxide on tumor growth. The mice in these studies are generally pre-exposed to UV radiation or a chemical that causes the development of the tumors; then the benzoyl peroxide is applied to the mouse skin. Some of these studies have found that benzoyl peroxide caused existing tumors on the skin to grow larger, but did not cause the development of new tumors. ⁶ In the vast majority of studies, benzoyl peroxide was not found to cause new tumors to develop. These mouse studies are often cited on websites that are trying to sell alternatives to benzoyl peroxide as evidence that benzoyl peroxide is a carcinogen. The results of the studies and their implications may be overstated and misinterpreted by these companies.

One article highlights the limitations of this line of research in mice for the application to safety assessment for humans: ⁷

The Food and Drug Administration (FDA) lists benzoyl peroxide as a category III substance (safety uncertain). However, the FDA concerns were not so extreme as to lead them to recommend discontinuing the use of benzoyl peroxide medications. ⁹ The FDA has called for additional research on the carcinogenic potential of benzoyl peroxide. According to the FDA, this research is currently being conducted.

The International Agency for Research on Cancer (IARC), which classifies substances based on carcinogenicity, has concluded that there is inadequate evidence for the carcinogenicity of benzoyl peroxide in humans and limited evidence in experimental animals for the carcinogenicity of benzoyl peroxide. The IARC does not categorize benzoyl peroxide as being carcinogenic; its carcinogenicity is labeled as being unknown. ¹⁰

References:

1. Cartwright, R.A., Hughes, B.R., Cunliffe WJ (1988). Malignant melanoma, benzoyl peroxide and acne: a pilot epidemiological case-control investigation. Br J Dermatol, 118(2):239-42.
2. Hogan, D.J., To, T., Wilson, E.R., Miller, A.B., Robson, D., Holfeld, K., Lane, P. (1991). A study of acne treatments as risk factors for skin cancer of the head and neck. Br J Dermatol. 125(4):343-8.
3. Iverson, O.H. (1994). Benzoyl peroxide and possible skin cancer risks in mice and humans. In Skin Cancer: Mechanisms and Human Relevance, CrC Series in Dermatology, (Mukhtar, H., Ed.) pgs 13-20.
4. Zbinden, G. (1988). Scientific opinion on the carcinogenic risk due to topical administration of benzoyl peroxide for the treatment of acne vulgaris. Pharmacol Toxicol, 63: 307.
5. LidAn, S., LindelAf,B.,& SparAn, P. (1990). Is benzoyl peroxide carcinogenic? Br J Dermatol., 123(1):129-30.
6. O'Connell, J.F., Klein-Szanto, A.J., DiGiovanni, D.M., Fries, J.W., Slaga, T.J. (1986). Enhanced malignant progression of mouse skin tumors by the free-radical generator benzoyl peroxide. Cancer Res. 46(6): 2863-2865.
7. Kraus, A.L., Munro, I.C., Orr, J.C., Binder, R.L., LeBoeuf, R.A., Williams, G.M. (1995). Benzoyl peroxide: an integrated human safety assessment for carcinogenicity. Regul Toxicol Pharmacol. 21(1):87-107.
8. Iverson, O.H. (1988). Skin tumorigenesis and carcinogenesis studies with 7,12-dimethylbenz[a]anthracene, ultraviolet light, benzoyl peroxide (Panoxyl gel 5%) and ointment gel. Carcinogenesis. 9(5):803-9.
9. http://www.fda.gov/c...PR_19950217.pdf
10. http://www.inchem.or...nzoylperox.html

Also:

Although issues regarding genotoxicity have been raised in the past, BP has now been labeled as GRASE (generally regarded as safe and effective) by the FDA, and all topical monotherapy products have been made available OTC since 2011. Labeling includes advice to avoid the eyes, lips, and mouth. The product can cause bleaching of hair and clothing, and risk of increased sunburn and the need for photoprotection also are mentioned. BP frequently causes dryness, erythema, and peeling upon initiation of treatment. Starting with lower concentrations (eg, 2.5%) and utilizing more emollient vehicles if needed can help alleviate these discomforts. Allergic contact dermatitis to BP occurs in 1 in 500 people and should be considered if a patient complains of itching and swelling of the eyes.

I think any chemical we apply to the skin (which is then absorbed) has the potential to put you at risk of cancer. BP also increases sensitivity to the sun, which is a direct link to skin cancer. This is why it is recommended to use a sunscreen all year round if using such treatments.

I personally wouldn't go back to using BP again. I did develop a few small moles on my face after using it and it made my skin very sensitive. That's just me though, I'm sensitive to most products.