Given the number of products in use, the state of knowledge about the hazards of dyes to human health is never likely to be complete. It is therefore prudent to minimise exposure to dyes of all types, even if no adverse health effects are known. Dyes known to be hazardous Some reactive dyes are recognised respiratory sensitisers. Breathing in respiratory sensitisers can cause occupational asthma. Once a person is sensitised, re-exposure to even very small amounts of the same dye may result in allergic symptoms such as a runny or stuffy nose, watery or prickly eyes, wheezing, chest tightness and breathlessness.
Some dyes can cause similar allergic skin reactions.
Certain reactive, vat and disperse dyes are recognised skin sensitisers. A small number of dyes, based on the chemical benzidine, are thought to possibly cause cancer. Substitutes exist for these dyes in textile use. Other dyes may also present hazards to health. It is essential to read the safety data sheet supplied with each hazardous product.