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Endocrine disruptors in hair dye: what science really says
What is an endocrine disruptor?
An endocrine disruptor (ED) is a chemical substance that interferes with the hormonal system. The French agency ANSES and the WHO recognize that chronic exposure to these substances is linked to fertility disorders, thyroid disruption and certain hormone-dependent cancers. Cosmetics represent a significant route of daily exposure.
The problematic substances in chemical hair dyes
Resorcinol — Classified as a proven endocrine disruptor by the French agency ANSES (2019 report). Present in almost all commercial oxidative hair dyes to stabilize the pigments. It is absorbed through the scalp during application.
PPD (paraphenylenediamine) — An oxidative synthetic dye classified as a strong allergen (category 1B) by ECHA. Studies associate repeated exposure to PPD with increased risks of bladder cancer (IARC meta-analysis 2010).
Ammonia — An irritant to the respiratory tract and the scalp. It promotes the penetration of other molecules into the hair fiber and the dermis.
What INSERM and ANSES say
The INSERM E3N study (2023), covering 98,000 French women, identified an association between frequent use of permanent hair dyes and the risk of hormone-dependent breast cancer (+23% among regular users). Since 2019, ANSES has recommended "reducing exposure to endocrine disruptors in cosmetic products", explicitly targeting resorcinol.
COSMOS Organic plant-based hair color: zero listed ED substances
The COSMOS Organic certification explicitly bans resorcinol, PPD, ammonia and hydrogen peroxide. Tresse Paris hair colors are composed of 6 tinctorial plants only, without any synthetic molecule. Formulation takes place in France under strict quality control, with complete traceability of all raw materials.
The COSMOS Organic certification explained →