Hair Dye

Dyeing your hair will give your baby birth defects

According to the American Cancer Society, about 70 percent of adult women use hair dye. So it only stands to reason that a significant number of pregnant women are going to be faced with the fact that they would be due for a reapplication while they’re pregnant. As with everything else in pregnancy, the question comes up as to what potential harm dyeing your hair might do to the fetus.

Many people, and many organizations, will tell you that dyeing your hair is dangerous for your baby. Hair dyes use harsh chemicals. Chemicals are absorbed through your head (or hands if you touch the stuff) and then seep into your blood, get carried to your unborn baby, and cause horrific problems like birth defects or cancer. (Right?)

You wouldn’t be crazy for thinking that hair dye could be bad for unborn babies. A widely publicized study was published in 2005, in the aptly named journal Cancer Causes and Control, which described a link between the use of maternal hair dye and the subsequent risk of neuroblastoma, a type of cancer, in their children.

Here’s the thing. That was a case-control study, and as we have discussed, that type of study is really susceptible to recall bias, where people remember things differently because they have a problem. Here’s how the study went. They telephoned over 500 mothers who had children with neuroblastoma. They asked the mothers about potential risk factors for cancer, including a lot of questions about hair dye use. Then they randomly called a similar number of people whose children did not have neuroblastoma and asked them the same question. They found that 23 percent of case mothers reported hair dye use, compared to 16 percent of control mothers. It is well known that people whose children have the disease (cases) are more likely to report stuff that might have caused the disease than people whose children don’t have the disease (controls). That’s recall bias. Moreover, you have to remember that this study does not prove that hair dye causes neuroblastoma; at best, it can show an association. The association was not even particularly strong.

The authors do note these limitations of the study, and ended the paper by calling for more research. There have been a number of studies of hair dye in pregnant animals. A study of twelve rabbits and twenty cats given hair dye many times during a pregnancy could find no effects in their offspring. Another study of five different hair dyes given to rats found no effects. This study also used a control of megadoses of vitamin A to prove that rats exposed to some compounds would have abnormal fetuses (they did). There are others, showing similar results.

Still, for some of you, any risk is too much. We understand that. But consider that you likely engage in many activities each day that are of higher risk to your baby than the theoretical and unproven one of dyeing your hair. For example, your risk of being in a car accident that would harm you and the baby is probably much higher than the risk from dyeing your hair. Talk with your doctor, and make your own decision. We know that dyeing hair is very important to some women (no names mentioned), and they should know there really is no evidence proving that dyeing their hair will cause cancer in their children.