They believe that it is not the henna itself that is the problem, but the compounds used as a solvent for the henna powder. Benzene, which is known to cause cancer, is banned for this purpose in many countries, but is still widely employed.

"The majority of the females in UAE routinely use henna to stain their nail, hands, feet and to decorate a large area of the skin of their arms and legs for cosmetic reasons," said the study, by a team from hospitals in the United Arab Emirates, published in the Leukaemia and Lymphoma journal.

"To our knowledge, the henna used at different henna salons in the UAE are actually mixed with benzene and other petroleum products in addition to many other chemical additives for colour enhancement.

"As the use of henna is restricted to females (most common among nationals), benzene and/or any of the other chemicals mixed in henna could be a possible risk factor."

Scientists have warned for years that some beauty products contain additives that have been linked to cancer. Henna has become popular because it is seen as a "natural" product.

But one popular type of liquid used to give a henna effect in tourist resorts around the world, so-called "black henna", is in fact not made of henna and often contains a substance called para-phenylenediamine which can cause allergies and scarring.

The Gulf, where henna application is a viewed as a cosmetic art form, uses real henna, but local authorities acknowledge that clinics often use pre-prepared pastes that have been mixed with benzene.

The journal study found that acute myeloid leukaemia was 93 per cent more common in Emirati women than Emirati men, and 63 per cent higher than in expatriate women. Normally, its incidence is higher in men.

"Benzene has always been known as a cancerous substance," said Dr Sherief Islam, one of the authors of the study. "It can be used as a solvent – in fact, if it's used in industrial paint there are strict health regulations about applying it."

A spokesman for the UK Department of Business said the use of benzene as a solvent was banned for all consumer products in Britain, and in particular for use in cosmetics, under European directives.