What are the possible dangers of benzoyl peroxide?

The benzoyl peroxide should be used with caution due to its various side effects. It is known to be a photosensitizer, a bleaching agent, and is strongly discouraged in certain specific cases.

• Benzoyl peroxide is a photosensitizing substance.

  The benzoyl peroxide is a photosensitizer, more specifically a phototoxic substance. Indeed, it causes immediate skin damage when exposed to UV rays, which generate free radicals whose accumulation leads to damage or destruction of cells. These reactions manifest as redness, similar to sunburn, or hyperpigmentation. They can vary in severity depending on skin sensitivity, concentration, quantity, and frequency of application of the benzoyl peroxide. It is recommended to use the product in the evening to avoid sun exposure and associated side effects.

• The use of benzoyl peroxide results in discoloration.

  Benzoyl peroxide should be used with caution to avoid any contact with the hair. It is recommended to apply it at least half an hour before bedtime, as its strong bleaching power can alter both colored fabrics and hair.

• Benzoyl peroxide is not recommended in certain cases.

  Benzoyl peroxide presents a moderate risk for the 9 months of pregnancy as well as breastfeeding. This is a precautionary measure as no study has yet demonstrated any harmful effect on the development of the fetus or the health of the mother. Finally, precautions should also be taken in children under 12 years of age, regardless of their weight.. Patients with wounds, fair skin, or using concurrent treatments with other keratolytic and detergent preparations should avoid the application of benzoyl peroxide-based products, as it may delay wound healing, increase photosensitivity in fair-skinned individuals, and intensify skin irritation in patients undergoing concurrent treatment.

Benzoyl peroxide generates benzene through degradation. However, benzene is a carcinogen for humans, classified by the International Agency for Research on Cancer (IARC).

Beyond its potential adverse effects on the skin, benzoyl peroxide is also suspected of being harmful to human health. A study revealed high concentrations of benzene in 111 samples of over-the-counter benzoyl peroxide-based products, analyzed by gas chromatography coupled with mass spectrometry. Among the products tested at room temperature, 34% showed benzene levels exceeding the 2 ppm limit, established for pharmaceutical products. To avoid the production of benzene, some dermatologists advise to store in a cool place creams based on benzoyl peroxide but are not overly alarmed about the dangers of this ingredient.

To assess the effect of sun exposure on the release of benzene by benzoyl peroxide, a second experiment was conducted by incubating a plate containing 54.5 mg of benzoyl peroxide at 37 °C (body temperature) under a UVA/B lamp for two and a half hours. The results show that sun exposure significantly increases the production of benzene. However, few in-depth studies have been conducted on this phenomenon. Other studies published in the journal have indicated notable differences in heat-induced benzene formation depending on the formulations of benzoyl peroxide-based pharmaceutical products. These results justify further research on other formulations to better understand the formation of benzene under the effect of UV rays.