The most common–and dangerous–of these chemicals is probably PPDs (p-Phenylenediamine), which has been linked to bladder cancer, lung, kidney and nervous system disorders and severe allergic reactions. Other chemicals to watch for include the following:
Resorcinol
This receives a nasty 8 out of 10 for hazard at the Cosmetics Safety Database. It is classified by the European Union as harmful, irritant to eyes and skin and dangerous for the environment. It may also disrupt hormonal function, and lead to hypothyroidism.
Ammonia
Ammonia is irritant to the skin, eyes and respiratory system, and can cause asthma and breathing difficulties. However, it is much less toxic than PPD, and only receives a rating of 3 out of 10 for toxicity at the Cosmetics Safety Database.
Persulfates
Sodium, potassium and ammonium sulphates are present in hair dyes and bleaches, and are used in concentrations of up to 60%. However, concentrations of only 17.5% have been shown to irritate skin, and persulphates are also toxic when the fumes are inhaled, causing asthma and lung damage. However, the Cosmetic Ingredient Review Expert Panel has concluded that they are safe for occasional use, provided that the skin is rinsed well after.
Hydrogen Peroxide
Hydrogen peroxide is used in hair bleaches. It is corrosive, and has been banned from cosmetic use in Japan and restricted in Canada. Animal studies have shown it has toxic effects on the nervous system, respiratory and digestive systems at low doses. Other studies on animals have also shown that hydrogen peroxide can damage DNA, possibly leading to cancer.
Lead acetate
This is present in some hair colouring products used for gradual darkening, and is another potentially toxic chemical. Lead has well-known damaging effects on the brain and nervous system.
4-ABP
This ingredient has been linked to development of cancer.
Worried your brand may contain some of these? A good tip for those living in the Americas would be to buy European or Japanese brands: the EU and Japan have banned many toxic ingredients that are still permitted elsewhere.
