Hair dye has been around for a long time - historians believe henna has been used for at least 5,000 years in India, the Middle East and North Africa.

The Queen of Sheba is said to have been decorated with henna, which is made from the dried leaves of a shrub, on her long journey to meet Solomon and, to this day, it remains a popular way of dyeing hair, finger nails, palms of hands and soles of feet.

Henna adds protection as well as volume but isn't permanent and can't offer the same choice of colours we get from modern man-made hair dyes.

In order to penetrate each strand of hair, these dyes contain strong chemicals. Hydrogen peroxide, for instance, helps to remove thenatural pigments, while ammonia opens the hair cuticle so new colour pigments can enter.

Chemicals in permanent dyes leave hair dry and lustreless and there is genuine concern they may enter the blood stream and present a health risk.

Synthetic chemicals are difficult to break down and may accumulate in the body. Some women complain about severe allergic reactions to their face and scalp.

A recent report in the International Journal of Cancer implies long-term use of hair dye is linked to bladder cancer.

Increased cancer risk was found only with permanent dyes, not semi-permanent or temporary hair colouring which rinse out after a series of washes.

Research shows some of the chemicals in hair dyes are absorbed through the skin of the scalp during application. Once absorbed, they may become concentrated in the bladder.

Dark hair dyes are the most worrying as they contain a higher concentration of man-made substances than lighter dyes.

It appears the risk is doubled if hair dye is used monthly for more than 15 years and it is highest in smokers who regularly use hair dyes.

Hairdressers should be aware of handling and breathing in the fumes of the chemicals and consider wearing a mask and heavy plastic gloves. Several studies have shown them to be at increased risk of developing cancer and leukaemia.

If you want to reduce your risk of chemical exposure when applying hair dyes, consider more gentle hair dyes with less aggressive contents.

I recently met Janine Carroll of Naturtint, based at Daventry, Northants, who explained their permanent hair colourant is low in peroxide and free of ammonia and resorcinol (all severe skin irritants).

It is also enriched with plant and cereal extracts such as oat, soy, corn, wheat and coconut which add extra shine and vitality.

She assured me the hair colouring is less harsh than mainstream brands, quick and easy to use, as well as dermatologically tested and manufactured to the highest standards.

Naturtint's semi-permanent range is free of ammonia, resorcinol, peroxide and PPD (p-phenylenediamine) and contain a sun filter to protect the hair.

Always do a skin patch-test before using any hair dyes, at least 48 hours before application.

Call Naturtint's special helpline on 0845 601 8129 with queries or visit