The Root Cause: Menstrual Irregularities and Hair Relaxers

Even though haircare products are offered to males and females, females form the majority target population for the haircare industry. The global haircare market was valued at USD 113.93 billion in 2025 and is estimated to grow at a combined annual growth rate of 7.46%. ¹ Haircare products can be categorized by their intended purpose, such as cleansing, changing appearance (hair dyes, straighteners etc.), and treatments (serums, oils, masks, etc.). Multiple epidemiological studies have reported that haircare product use increases the risk of benign and malignant gynecologic conditions.^2–13

The female reproductive system undergoes regular cyclic changes under the controlled interplay of hormones (follicle-stimulating hormone, luteinizing hormone, estrogen, and progesterone) in periodic preparation for ovulation and potential pregnancy. ¹⁴ Approximately 10–30% of menstruators are affected by abnormal uterine bleeding (AUB), described as alterations in frequency, duration, or volume of menstrual blood loss. ¹⁵ Dysmenorrhea (recurrent menstrual pain and cramping) affects 60–91% of adolescents ¹⁶ and 16–29% of all menstruators. ¹⁷ The complex nature of the menstrual cycle is controlled through positive and negative feedback mechanisms that exist in the hypothalamus-pituitary and ovarian (HPO) axis. ¹⁵ The endocrine-disrupting chemicals (EDCs) can alter the internal controls and lead to menstrual irregularities.^18,19 Moreover, the female sex hormones are involved in the etiopathogenesis of most benign and malignant gynecologic conditions.

In this issue of the Journal of Women’s Health, a new epidemiologic study by Dr. Geller and colleagues reported on the association between the use of chemical hair straighteners and menstrual disturbances among the PRESTO study participants. ²⁰ The data suggest that among North American individuals, current (vs. never) use of chemical hair relaxers was associated with higher prevalence of AUB and dysmenorrhea.

Chemical hair relaxers are products that straighten curly hair and can be broadly classified into “lye” relaxers (sodium hydroxide), no-lye (calcium hydroxide) relaxers, and “thio” (ammonium thioglycolate) relaxers.^21,22 Many hair relaxers have EDCs such as parabens, heavy metals, phthalates, formaldehyde, para-phenylenediamine etc.^7,23–25 that possess the biological ability to alter endocrine homeostasis of the HPO axis. ¹⁸ EDCs are known to affect hormone levels not only by disrupting hormone functions by binding to nuclear hormone receptors but also by affecting genes and their transcriptional co-activators, enzymatic pathways involved in steroid biosynthesis and metabolism. ¹⁸

The lifetime prevalence of hair relaxers use ranges from 52% to 94% among Black women, 15% to 45% in Hispanic women and those of other minoritized racial and ethnic groups, and approximately 5% among non-Hispanic white women in the United States.^26–28 Eurocentric beauty norms and race-based-discrimination are some of the factors that further precipitate the social and race-based use of hair straightening products among the races with naturally curly hair.^29,30 This epidemiological trend is worth exploring further as there is biological plausibility that EDCs present in hair relaxers could potentially lead to gynecological pathologies.^18,19

The U.S. Food and Drug Administration (FDA) does not require hair products manufacturers to file their product formulation with the FDA. There are exceedingly low barriers to the manufacturer of haircare products to demonstrate the safety of individual products or ingredients except for color additives that are prohibited or restricted. ³¹ Lack of regulation makes it difficult to identify all these subcomponents/ingredient lists of haircare products. Hence, there is a critical need to identify and document endocrine-disrupting chemicals in haircare products. Additionally, there is a gap in descriptive epidemiological, large-scale use data about the frequency and duration of use of haircare products. One way to collect these data is to curate interval surveys that can be sent to large populations to gather this information over extended periods of time.

There’s also subjectivity in the collection of menstrual data. Lack of universal standardization in data collection on a large scale makes it more difficult. Additionally, there is generational stigma that surrounds menstrual issues, particularly menorrhagia and dysmenorrhea. The normalization of these conditions leads to underreporting of these symptoms. The quantification of menstrual blood loss can be especially challenging since we don’t have a universally adopted, patient-centric, and clinically practical measurement method. However, longitudinal collection of menstrual cycle data can be a good marker to evaluate the reproductive function of an individual and has been described by some as the fifth vital sign.

Haircare products, due to their potential for long-term use and likelihood of increased absorption through the skin and scalp, make them an easier product to enter systemic circulation.^32,33 Multiple high-quality epidemiologic studies reporting similar trends in the use of haircare products and increased risk of gynecologic conditions should raise concerns about the components of haircare products. These insights highlight the need for systemic screening of haircare product ingredients to be more regulated. Consumer awareness should also be raised to allow for informed decision-making regarding the components of their regularly used haircare products.

Styling one’s hair should not come with the high price of endocrine issues.