Association of Hair Dye Use With Circulating Levels of Sex Hormones in Premenopausal Japanese Women

The study examined the relationship between hair dye use and sex hormone levels in 431 premenopausal Japanese women. It found that long-term use of permanent hair dyes was associated with a 17% increase in plasma total testosterone levels compared to non-users. Additionally, frequent use of non-permanent hair dyes was marginally linked to higher total and free estradiol levels. The study suggested that chemicals in hair dyes, such as resorcinol and α-naphthol, might have endocrine activity, potentially leading to these hormonal changes. However, the increase in testosterone was considered too small to impact breast cancer risk. The study emphasized the need for further research on the hormonal effects of hair dye use.