Depigmentation with tert-butyl hydroquinone using black guinea pigs

Area of Science:

• Toxicology
• Dermatology
• Cosmetic Science

Background:

• Tert-Butyl hydroquinone (TBHQ) is widely used in consumer products with potential for human dermal exposure.
• Assessing TBHQ's safety is crucial due to its common applications and direct skin contact.
• Previous safety data on TBHQ's dermatological effects, particularly pigmentation changes, is limited.

Purpose of the Study:

• To evaluate the potential of TBHQ to induce skin depigmentation following repeated dermal application.
• To establish a dose-response relationship for TBHQ-induced pigmentation changes in a relevant animal model.
• To compare the effects of TBHQ with known depigmenting agents like Hydroquinone (HQ) and Hydroquinone monomethyl ether (HQMME).

Main Methods:

• Repeated dermal application of TBHQ, HQ (positive control), and HQMME (positive control) to black guinea pigs over 13 weeks.
• Testing TBHQ and HQ at concentrations of 0.1%, 1.0%, and 5.0%; HQMME at 10.0%.
• Weekly and final evaluations of skin for depigmentation, hyperpigmentation, and irritation, including post-depilation assessment.

Main Results:

• TBHQ and HQ at 1.0% and 5.0% caused slight to moderate skin irritation; 0.1% showed weak irritation.
• Depigmentation was observed in 20-40% of animals treated with 1.0% and 5.0% TBHQ or HQ.
• HQMME induced complete depigmentation in all treated animals; hyperpigmentation was noted across most groups.

Conclusions:

• TBHQ induces dose-dependent depigmentation in black guinea pigs at concentrations of 1.0% and higher.
• A no-observed-effect level (NOEL) for TBHQ-induced depigmentation was established between 0.1% and 1.0%.
• TBHQ demonstrates depigmenting potential, necessitating careful consideration in product formulations with dermal exposure risks.