Roughly half of women and about 10 percent of men over the age of 40 dye their hair. But no matter how safe companies claim their products are, there are still questions about what all of those chemicals do to someone’s long-term health. In particular, can years of permanent hair-dyeing increase a person’s risk of developing cancer?
Smaller studies have produced a variety of results over the years, but a new and much more comprehensive survey is providing a more complete answer. However, not all hair dye is created equal, and it’s important to understand what’s on the market before diving into the research.
What’s the Difference Between the Major Types of Hair Dye?
When reviewing any research results, it’s critical to know what sort of hair dye these studies are looking at. The majority of them are inspecting permanent hair dye, which uses ammonia to change someone’s natural hair color and can last for months at a time. In contrast, semi-permanent hair dye doesn’t use ammonia, but it fades much more quickly, usually within four to 12 washes.
Natural hair dye, another popular option, tends to use fewer chemicals, but it isn’t fully chemical-free. Additionally, natural dyes tend not to last as long or be as vibrant as conventional dyes, which means some users may end up dyeing their hair more frequently to keep up their new color.
What Does the Science Say?
Over the decades, researchers have gotten conflicting results in the quest to figure out if different hair dyes, especially permanent dyes, increase someone’s risk of cancer. Because there are so many types of dyes and over 5,000 different chemicals in dyes across the board, it’s hard to isolate products and figure out the specific health effects of individual chemicals.
However, a much more expansive study from Harvard Medical School that was published in The BMJ looked at permanent hair dye usage survey data from over 117,200 participants. Researchers collected the data over the course of 36 years, beginning all the way back in 1976. The analysis took a number of factors from hair dye users into account, including age, race, body mass index, risk factors for certain types of cancer, and lifestyle habits like smoking and alcohol use. The research also investigated permanent hair dye routines, including frequency of dyeing, number of years spent dyeing, age of first use, and more.
The study concluded that hair dye users did not have an overall higher cancer risk or risk of cancer-related death than non-dye users. However, there were a few irregularities. Long-term hair dye users had a slightly higher risk of basal cell carcinoma, which is the most common type of skin cancer. Specific ovarian and breast cancers were also more likely in hair dye users.
That said, researchers were quick to point out that more work would need to shed light on these associations to see if they were in fact related. The survey data, which was taken from the larger Nurses’ Health Study, also focused mostly on white female nurses, so the results aren’t as conclusive for men or people of other races. Moreover, the original survey didn’t go into detail about the individual permanent dye products used, and some respondents could’ve mistaken their semi-permanent or natural dye for a permanent one.
Even with these results, it’s still important to ask questions about the specific hair products you’re using and to understand what’s going onto your hair and scalp. It never hurts to have more information.