Most American women, as well as many men, have dyed their hair at one time or another. People all over the world change their hair color. Men often use “progressive dyes,” such as Grecian Formula, and women may use semi-permanent dyes such as henna. But most dyeing (70 percent of market share—and the kind we are talking about here) is done with permanent colors: You bleach out the pigment and simultaneously add whatever color you want, which is absorbed by the hair shaft. Permanent hair dyes have been the subject of scientific study for decades. Do they promote cancer of any kind? That’s been the main worry. You will find sites on the Internet telling you they do.
It’s impossible to prove that anything is completely safe. Still, most good studies have failed to find a clear link between today’s hair dyes and cancer.
There are many chemicals in hair dyes, but the ones that have attracted the most scientific attention are aromatic amines, which in lab animals have been shown to increase the risk of cancer or genetic mutations. Results have been inconsistent in humans, however. Some studies have suggested that hairdressers, because of their higher long-term exposure, are at slightly increased risk for cancer, but other studies have not.
There are many variables: the number of times over a lifetime the dyes were used, for instance, and the color (black and dark brown have greater concentrations of chemicals). Bleach is not a culprit. In the late 1970s, hair-dye makers removed some chemicals thought to be potentially dangerous. One study did find a slightly increased risk of lymphoma among women who started dyeing their hair regularly before 1980.
The American Cancer Society has concluded that most studies have not found that hair dyes pose a significant cancer risk. However, it says, more research is needed on the long-term use of the darker shades, as well as occupational exposure (in hairdressers).
If you dye your hair, follow the package instructions. Do the patch test to make sure you are not allergic or have not become allergic to any ingredients. Wear plastic gloves; most packages provide them. Don’t leave the dye on your hair longer than directed. Rinse thoroughly. You might try henna or other nonpermanent dyes, but these don’t cover gray as well.