In Europe, PPD levels are allowed to form 6 per cent of total content, except in Germany, France and Sweden where it has been banned completely.

Despite its restricted use, dermatologists continue to report increasing numbers of cases of contact dermatitis. In one recent survey in London, contact dermatitis cases had doubled in the past six years, and researchers are convinced that permanent hair dyes are to blame. The same clinic has confirmed the trend over an even longer period. Between 1965 and 1975 it would see up to 11 patients a year who had non-occupational PPD allergy (that is, they weren’t hairdressers). But in recent years that figure has increased to 40 cases each year.

There’s been a similar trend reported in Belgian and Portugal, as well as in Denmark, and Germany, despite the PPD ban.

The problem is far worse in the Far East, where hair dyeing is extremely popular, and with brands that don’t have a PPD restriction. One study in Thailand has reckoned that more than 1 million adults may be sensitive to PPD.

(Source: British Medical Journal, 2007; 334: 220).