According to a recent study from the National Institute of Health, women who used chemical hair-straightening products are at a higher risk for uterine cancer. The study followed over 33,000 women for nearly 11 years, and during that time 378 uterine cases were diagnosed. The woman who reported frequent use, meaning more than four times per year, were more than twice as likely to develop uterine cancer than those who did not use the products.