A new study in the American Journal of Epidemiology has linked the potentially harmful chemical exposure from hair relaxers to the incidence of uterine fibroids in women and early puberty in young girls.

According to the study published from researchers at Boston University, the use of chemical hair relaxers may be the cause of the high incidence of fibroids in black women or women of African ancestry.

Uterine fibroids, also known as uterine leiomyomata, are benign tumor, which means they are not cancerous, that grows on the walls of the uterus of a woman. It is most common in women of African descent and in women who have not given birth between the ages of 30 and 45 years old.

In more recent times, though, women much younger than 30 have been diagnosed with fibroids. Fibroids can be as small as a pea and can grow as large as a melon. It is estimated that 20-50% of women have, or will have, fibroids at some time in their lives.

The study, which was led by Dr. Lauren Wise of Boston University’s Slone Epidemiology Center, tracked the lives of more than 23,000 pre-menopausal Black American women from 1997 to 2009 and found that the two- to three-times higher rate of fibroids among black women may be linked to chemical exposure through scalp lesions and burns resulting from relaxers.

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Also, the study points out that a significant majority of African-American women who were diagnosed with uterine fibroids also admitted to using chemical relaxer treatments on their hair at some point.

Researchers say chemical hair relaxers products may contain hormonally active chemicals, like parabens and phthalates which according to them have been known to cause harmful estrogenic effects on the cells of animals.

The researchers also found that women who got their first menstrual period before the age of 10 were also more likely to have uterine fibroids.

In a sample that included African, Caribbean, Hispanic, and White women, the average age of a woman’s first menstrual period varied anywhere from age 8 to age 19, but in African-American women, who were more likely to use chemical hair relaxers, the onset of menstruation came at a much earlier age.

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While the study stayed clear of making any assertions, many have pointed out that the activities of the cosmetic industry, including the ingredients of chemical hair relaxers, are not regulated by the U.S. Food and Drug Administration.

The report points out that laboratory analysis of the ingredients of chemical hair relaxers showed that the active ingredient in “lye” relaxers is sodium hydroxide, which is potentially harmful to body tissues and can cause dermatitis, lesions, hair loss, chemical burns, and skin irritation. In addition, hair relaxers are known to contain hormonally active compounds, such as parabens and phthalates.

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The study also suggested that some of the chemicals in hair relaxers, including phthalates which can be absorbed by the skin through lesions or “relaxer burns,” have been shown to have harmful estrogenic effects on the cells of experimental animals.