Azo dyes are the largest family of synthetic colourants used on textiles, and most of them are legal to use. The EU restricts the subset that can break down to release certain aromatic amines, some of which are carcinogenic, and under REACH Annex XVII a textile article that may come into contact with the skin must not release those listed amines above 30 mg/kg.
In practice this is why dark cotton and viscose shades from India are routinely tested for azo amines before shipment. It is not a ban on azo dyes as a class, but a limit on what the finished textile can release. Several other markets apply similar restrictions, so the test is worth running even on orders that are not bound for the EU.
How azo dyes work and where the risk comes from
Azo dyes share a chemical structure that gives strong, bright colours cheaply, which is why they dominate the dyeing of cotton, viscose, polyester and wool. Under reducing conditions, such as those found on the skin with sweat and bacteria, some azo dyes split at the azo bond and release the amine they were built from. If that amine is one of the listed carcinogenic amines, the dye is the problem.
The risk is in the choice of dye, not in dyeing itself. Reputable dye manufacturers stopped making the restricted dyes years ago, but cheaper dyestuffs, mixed or unlabelled lots, and small dyehouses buying on price can still bring them into the supply chain.
Where azo amine failures come from
- Low-cost direct and acid dyes bought from unbranded suppliers.
- Black and navy shades, which use the most dye and are most often made by mixing.
- Printed fabrics, where the printer's pigment paste is sourced separately from the mill's dye.
- Trims, threads and labels dyed by a different sub-supplier from the body fabric.
Testing and prevention
The test for azo amines is a chemical analysis of the finished fabric performed by a lab; it cannot be done visually or by the mill's quality team. Test each shade and each dyeing route, since a pass on one colour says nothing about another. Ask the dyehouse for dye supplier declarations as a supporting document, but treat the lab report on sealed bulk samples as the evidence. Where a shade fails, the usual remedy is to re-dye with a conformant dye from a known manufacturer and retest, which costs time rather than the order, so allow for it on dark shades with a new dyehouse.
Requirements differ between markets and change over time, so confirm current limits and methods with an accredited lab or your compliance team. This is general information, not legal advice.
How we handle azo testing
We agree with you which shades and components need azo amine testing for your market, then draw sealed samples from the bulk and send them to an NABL-accredited or international lab. We check the report against your spec before loading and supervise the loading. You get a weekly update, and a free 20-minute sourcing review is available if you want to talk through a dyed or printed programme before you place it.