A growing number of people are suffering from allergies to hair dye, according to researchers.
Over 66 per cent of hair dyes contain para-phenylenediamine (PPD), which is known to cause allergic reactions and has been banned in some European countries in the past.
Writing in this week's British Medical Journal, researchers from St Thomas' Hospital in London warn that allergic reactions can lead to dermatitis on the face and even facial swelling.
Lead researcher Dr John McFadden told the BBC that hair dye allergy could present with mild or severe symptoms, ranging from "tingling or discomfort" to "redness and swelling of the forehead, ears, neck and eyelids".
A recent survey in London revealed a doubling in frequency of positive reactions to PPD to 7.1 per cent in adults and, with numbers of people using hair dyes increasing, there are concerns that the frequency of allergic reactions will rise.
However, there are no widely accepted alternatives for use in permanent hair dye and current legislation allows products to contain up to six per cent PPD.
The authors insist that wider debate on the composition of hair dyes is overdue as allergy clinics are increasingly being burdened with the problem.
What's better? Private or NHS healthcare?