Allergic reactions to hair dye are on the increase, researchers have warned.

According to a report in the British Medical Journal, allergic reactions are increasing as more and younger people opt to use hair dye. This can lead to dermatitis on the face and in severe cases, facial swelling.

The researchers noted that more than two-thirds of hair dyes currently contain para-phenylenediamine (PPD) and other related agents. During the 20th century, allergic reactions to PPD became such a serious problem, it was banned from hair dyes in Germany, France and Sweden.

Current EU legislation allows PPD to comprise up to 6% of the constituents of hair dyes on the consumer market. However no satisfactory or widely accepted alternatives to these agents are available for use in permanent hair dye.

The researchers said that anecdotally, dermatologists in the UK have reported that the frequency of positive reactions to PPD following patch testing is increasing. This trend has also been observed in other countries.

They also highlighted the fact that market research indicates that more people are dyeing their hair and are doing so at a younger age. For example, a Japanese survey carried out in 1992 found that 13% of female teenage school students, 6% of women in their 20s and 2% of men in their 20s reported using hair colouring products. By 2001, these figures had increased to 41%, 85% and 33% respectively.

The researchers also noted that severe hair dye reactions have recently been recorded among children.

"Wider debate on the safety and composition of hair dyes is overdue. Cultural and commercial pressures to dye hair are putting people at risk and increasing the burden on health services", the researchers said.

However they acknowledged that it may not be easy to reverse these trends, as some patients have continued to use such dyes, 'even when advised that they are allergic to them and risk severe reactions'.