People who use hair straightening chemicals could be at significantly higher risk from womb cancer, a study has shown.
Most chemical straightening - also known as hair relaxing - is the process of breaking protein bonds in the hair and is commonly used by black women.
Researchers tracked 33,947 racially diverse women, ages 35 to 74, for an average of nearly 11 years.
During that time, 378 women developed uterine cancer.
Study leader Alexandra White of the U.S. National Institute of Environmental Health Safety (NIEHS) said in a statement: "We estimated that 1.64% of women who never used hair straighteners would go on to develop uterine cancer by the age of 70, but for frequent users, that risk goes up to 4.05%,"
"However, it is important to put this information into context. Uterine cancer is a relatively rare type of cancer".
Womb cancer is the most common gynaecological cancer in the United States, according to the Centers for Disease Control and Prevention (CDC), with rates rising, particularly among black women.
It comes after earlier studies showed hair straighteners contained so-called endocrine disrupting chemicals, which have been associated with higher risks of breast and ovarian cancer.
Reflecting on the new findings, a team of scientists wrote in The Journal of the National Cancer Institute: "These findings are the first epidemiologic evidence of association between use of straightening products and uterine cancer"
"More research is warranted to ... identify specific chemicals driving this observed association."
Womb cancer affects one in 36 women in the UK in their lifetime, and recent research in this country has suggested that obesity causes around a third of the cases.
The study, funded by Cancer Research UK, found that for every five extra body mass index (BMI) units, the risk of a woman developing womb cancer is increased by 88%.
- An earlier version of this story referred to 'chemical straightening' simply as 'hair straightening' and used incorrect images to illustrate this. This has since been corrected.
