What are azo dyes and why are they banned in some countries?

Azo dyes are a large class of synthetic dyes that account for roughly 60-70% of all dyes used in the textile industry. While most azo dyes are safe, a subset of approximately 24 specific azo dyes can break down and release aromatic amines that are classified as carcinogenic. These restricted amines include benzidine, 4-aminobiphenyl, and o-tolidine, all of which are linked to bladder cancer.

The European Union banned these 24 carcinogenic azo dyes in textiles through the REACH regulation, and similar restrictions exist in Japan, China, and India. However, the United States has no federal regulation restricting azo dyes in clothing. This means garments sold in the US market, particularly from fast fashion brands with global supply chains, may contain restricted azo dyes that would be illegal to sell in Europe.

Azo dyes can transfer to skin through sweat and friction, making skin contact a direct exposure pathway. Dark-colored and brightly colored garments tend to use higher dye concentrations. Choosing OEKO-TEX or GOTS certified clothing ensures that restricted aromatic amines from azo dyes have been tested for and excluded. ONDU prioritizes brands with these certifications for your protection.