Does  long-term use of permanent hair dye increase your risk of cancer?  In 1979, the FDA  asked companies to put warning labels on hair dyes containing coal-tar derivatives that had been found to cause cancer in lab animals. Instead, manufacturers voluntarily removed the ingredients

In fact, no study has ever presented strong evidence linking permanent hair dye to cancer in humans!  Most experts even say you can keep coloring during pregnancy.  However, one should try to not dye their hair as much (since you can never be too safe).   Sharon Dorram-Krause, head colorist at John Frieda Salon in New York City, advises pregnant clients to consider getting only highlights (to keep chemicals off the scalp) or using weaker, semipermanent dyes.