Hair Products are Linked to Cervical Cancer

An investigation developed by the Intramural Research Program of the National Institute of Health and the National Institute of Environmental Health Sciences of the United States raised the hypothesis that endocrine disruptors (EDC), chemicals capable of mimicking hormones and altering the correct functioning body, could influence the risk of uterine cancer.

To do this, they examined 33,947 women between the ages of 35 and 74, including sisters, who still had a uterus at the time of enrollment in the study. The research ran from 2003 to 2009. The findings revealed that women who used straightening products frequently were twice as likely to develop uterine cancer.

The interest arose because uterine cancer is one of the most frequent types of gynecological cancer in women. Over the past two decades, influenza and death rates have increased in the United States, with more than 65,950 new cases and 12,550 deaths through 2022, the study said. This research confirmed that the components of hair products, including formaldehyde and paraphenylenediamine, have played a potential role in the development of this disease.

In fact, it is not a hidden issue. For example, this year there was the case of the British multinational Unilever, which was forced to withdraw several brands of dry shampoo from the market, due to the possible existence of a high amount of benzene, another component that can cause cancer.

However, during the study process, they had to withdraw approximately 16,393 participants for various reasons. These include having an uncertain history of uterine cancer, undergoing a hysterectomy or removal of the uterus prior to enrollment, failing to provide information about the use of hair products, or simply voluntary withdrawal.

On the other hand, during the beginning of the research, the participants were asked to complete a form about the consumption of hair products in the last 12 months. There they found response options that include “1-2 times a year”; "I did not use"; “every 3-4 months”; "once a month"; and “more than once a month”. The color of the dyes (“dark”, “light”), the duration of use (“not used”, “less than 5 years”, “5-9 years” and “10 years or more”).

Participants responded to the frequency of use of 7 hair products, including semi-permanent, permanent, and temporary hair dyes, straightening or straightening products, and permanent wave hair.

In addition, physical activity was taken into account, if tobacco is consumed (“never”, “past”, “current”); alcohol consumption (“never”, “past”, “current-drink per day”); educational level (“high school or less”, “some college”, “college and above”); and work history in beauty salons or barbershops.

On the other hand, reproductive history was also evaluated, including age at first menstruation (“under 13 years”, “13 years and over”), menopausal status (“premenopausal” and “postmenopausal”), use of oral contraceptives (“none”, “<2, 2 years <10, ≥10 years”), number of children (“0”, “1”, “2”, “≥3”) and the use of replacement therapy hormonal (“none”, “estrogen only”, “estrogen plus progesterone, but never estrogen alone”).

Even during the study they used the Wald tests. A parametric statistical test to determine whether associations between uterine cancer and employment hair products varied by ethnicity, obesity, and physical activity. And in the case of the ages of 70 years, the Breslow method was used. Which is a measure of the thickness of a melanoma, or a form of skin cancer that starts in cells. This method was performed with the purpose of estimating the cumulative risk of developing uterine cancer in elderly women.

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Also, during the study, the histological codes of the International Classification of Diseases (Oncology 3) were used to define cancer of the tissue that covers the interior of the uterus, better known as the endometrium. There, they classified them into type I and type II. Which, type I endometrial cancers are more sensitive to hormones, having a higher expression of estrogen receptors; they tend to have better survival outcomes. While type II estrogen cancers are clinically more aggressive and have a poor prognosis.

On the other hand, other variables collected at the start of the study included age and ethnicity (African American/Black, Hispanic/Latino, Hispanic/Latino non-Black, Asian Pacific Islander, or American Indian).

Results and conclusions

Ultimately, during the investigation period, 378 women were identified who reported a diagnosis of uterine cancer after enrollment. Of which, 262 cases of uterine cancer were medically confirmed, that is, 94.7% of the cases presented. The association between the development of uterine cancer and hair straightening products was evident. However, it did not happen with the products to make waves or with the dyes.

It was concluded that women who ever used hair straighteners were predominantly African American/Black (59.9% of the study) and tended to be younger, with a higher body mass index (BMI) and with less physical activity than those who never used. These results and conclusions, beyond the revealing health results, lead us to think that there are several factors that influence the frequent use of hair straightening products. Like Eurocentric beauty standards, the social pressures exerted on black and Latin women in the workplace, and the threat of discrimination coupled with the whim of changing their hairstyle and image.