Women who use permanent hair dye products, kindly take note. Researchers have found that permanent hair dye can slightly increase the risk of some types of breast, skin and ovarian cancer.The study from Harvard University in the US, published in the journal The BMJ on Thursday, also revealed that natural hair colour was also found to impact on the likelihood of some cancers.Use of hair dye is very popular, particularly among older age groups keen to cover up signs of grey. For example, it is estimated that it is used by 50-80 per cent of women and 10 per cent of men aged 40 and older in the US and Europe.While the World Health Organisation's International Agency for Research on Cancer has classified occupational exposure to hair dyes as a probable carcinogen, there is no warning about personal use because existing evidence is inconclusive.To gain a better understanding of the risk of cancer from use of personal hair dye, researchers analysed data on 117,200 women from the Nurses' Health Study, which includes assessments of hair dye exposure.The women did not have cancer at the start of the study and were followed for 36 years.Ever use of permanent dyes was associated with a slightly increased risk of the basal cell carcinoma of the skin, and this risk was higher in women with naturally light hair.The results showed an increased risk of three types of breast cancer -- estrogen receptor-negative, progesterone receptor-negative, and hormone receptor-negative -- and ovarian cancer was also linked to use of permanent dyes, with risk rising according to the cumulative amount of dye women were exposed to.An increased risk of Hodgkin lymphoma was also seen with the use of permanent hair dye but only for women with naturally dark hair."Possible explanations could be that shades of permanent hair dyes are associated with the concentration of ingredients, with darker colours having higher concentrations," the study authors said.However, the results showed no increased risk of most cancers or of cancer death in women who reported having ever used permanent hair dyes compared with those who had never used such dyes.The authors also pointed to some limitations, including the lack of racial diversity of study participants and the possibility that other unmeasured factors, such as use of other products, may have affected the results.Nevertheless, the authors said their findings "offer some reassurance against concerns that personal use of permanent hair dyes might be associated with increased cancer risk or mortality."