An official with the ministry warned that the public should carefully read labels and instructions of the hair dye products before they dye their hair.

He said most ingredients of hair dye products contain allergenic chemicals and allergic reactions occur according to the sensitivity of the consumer's body, which might range from partial allergy to large-scale allergy.

The official cited evaluation result by the International Agency for Research on Cancer (IARC) in Lyon, France that there's no sufficient evidence to prove the link between hair dye and carcinogencity.

The official also cited the findings of the Cosmetic Ingredient Review (CIR), a program supported by the Cosmetic, Toiletry and Fragrance Association (CTFA) in the United States, that the commonly used chemical hair dye, paraphenylene-diamine (PPD), leads to allergies but animal tests and epidemiological data show that PPD does not lead to malformation or cancer.

Last week, state media reported that the death of a Chinese woman who died of leukemia might be linked to her long term hair dying. Beijing Daily Messenger reported that chief doctor of the hematology department in Beijing Friendship Hospital found that the patient's frequent hair dye, about once every three months, might caused the leukemia.

Wang was quoted that mainland researchers found that people who dyed their hair were 3.8 times more likely to develop leukemia, because PPD could enter the bloodstream through the scalp and then pass into bone marrow.

The official with the Health Ministry said China exerts strict supervision over hair dye products, where hair dye products are regarded as special cosmetics, which must pass a series of tests including toxin tests, chemical safety tests and risk evaluation of an expert panel.

The Health Ministry issued a list of hair dye ingredients that made restrictions of ingredient use and rules of labeling. Ingredients that were not on the list are banned by the ministry in hair dye products. The list, which came into effect on January 1, 2006, will change the list according to latest scientific findings.

A note of warning of possible allergies and a pre skin test is demanded on the label by the ministry.

The ministry will conduct crackdown on illegal use of banned chemicals in hair dye products this year, the official said.