Exposure to the chemicals in hair products increases your risk of developing uterine cancer.
Women who used straightener products in the previous 12 months have been found to have an 80% higher risk of developing uterine cancer according to research published in the Journal of the National Cancer Institute.
US researchers reviewed records of 34,000 women aged 35-74 who reported on hair product use over a 12-month period between 2003 and 2009. They also looked at age, ethnicity, alcohol consumption, smoking status, height, weight, physical activity, education level, reproductive history, and occupational history such as working in hair salons.
The women were followed up annually for an average of around 11 years, with in-depth follow up every three years.
None had uterine cancer at the start of recording and 378 women reported a diagnosis of endometrial cancer, uterine sarcoma, or other type of uterine cancer over the follow-up period.
When compared with those who did not use hair straightening products in the last 12 months, frequent users (more than four times per year) had an 80% increased risk of developing uterine cancer. The rate of uterine cancer incidence in the United States is around 27.8 new cases per 100,000 women per year according to the National Cancer Institute.
“There was a monotonic exposure-response relationship with increasing frequency of use of straighteners,” the authors said.
Associations between product use and uterine cancer were assessed using Cox proportional hazards models and adjusted for self-reported factors such as ethnicity, BMI, menopausal status, oral contraceptive use and hormone replacement therapy.
Previous studies have found links between hair products and both breast and ovarian cancer, but a clear epidemiological link to uterine cancer was not noted until now.
Because estrogen and progesterone imbalances in women have been shown to be a risk factor for uterine cancer, it was hypothesised that endocrine-disrupting chemicals (EDCs) which alter hormone activity contribute to uterine cancer, the authors explained. Many hair products in use today globally not only exposed women to EDCs but could also contribute to carcinogenesis, they added.
“Straightener use may cause scalp lesions and burns, which facilitates the permeability of chemicals through the scalp. Heating processes such as flat ironing or blow drying during straightening treatments could release or thermally decompose chemicals from the products, leading to potential higher exposures to hazardous chemicals among the users,” the authors said.
No association was found between use of hair dyes and an increased risk of uterine cancer.
The researchers said identifying the specific chemicals driving the observed association between straightening products and uterine cancer would be the next step.