Chemical hair straightening products used by millions of Americans may double the risk of womb cancer, an official study suggests.
Research carried out by the National Institutes of Health (NIH) looked at 33,000 women across the US for more than a decade.
The rate of uterine cancer was 4.05 per cent in women who used straightening product four or more times a year, compared to 1.64 per cent in those who did not.
Scientists believe the chemicals in the creams seep into the bloodstream through the scalp and travel to the womb.
Uterus cancer is uncommon, making up only around three per cent of all cancer diagnoses in American women annually.
But researchers warn rates have been rising in the US in recent years, particularly among black women.