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In vitro and in vivo percutaneous absorption of catechol
C T Jung1, R R Wickett, P B Desai
1U.S. Food and Drug Administration, Office of Cosmetics and Colors, Laurel, MD 20708, USA. cjung@cfsan.fda.gov
Summary
Safety data for catechol in permanent hair dyes is insufficient. Studies show minimal skin absorption from hair dye but significant absorption when applied in ethanol, indicating potential risks.
Area of Science:
- Toxicology
- Dermatology
- Cosmetic Science
Background:
- The Cosmetic Ingredient Review Expert Panel noted insufficient data regarding the safe use of catechol in permanent hair dyes.
- Key data gaps included the extent of catechol oxidation and skin absorption.
Purpose of the Study:
- To assess the percutaneous absorption and fate of catechol in skin.
- To evaluate catechol safety in the context of permanent hair dye formulations.
Main Methods:
- In vitro and in vivo percutaneous absorption studies using human and rat skin.
- Hair dye formulations spiked with catechol (0.6%) and catechol in ethanol (4%) were used.
- Skin absorption, oxidation, and systemic absorption were measured over time.
Main Results:
- Short exposure (30 min) to catechol in hair dye resulted in minimal absorption (0.4% human, 0.2% rat skin).
- Higher concentrations (4%) in ethanol showed significant absorption (81% in vitro, 53% in vivo after 24h).
- Skin catechol levels remained stable for 72h, indicating no significant skin reservoir effect.
Conclusions:
- Catechol absorption from permanent hair dye is minimal due to short exposure and oxidation.
- Higher concentrations of catechol in ethanol demonstrate substantial skin penetration, raising safety concerns.
- Further research is needed to fully ascertain the safety of catechol in hair dye products.