Hair dye dilemmas - includes related article on permanent eyeliner

FDA Consumer, April, 1993 by Margie Patlak

Many graying baby boomers find themselves lingering in the hair dye aisles of drugstores, wistfully eyeing boxes displaying the colors their hair once was.

Members of the 40-plus generation are not the only ones who change theft hair color. The Cosmetic, Toiletry, and Fragrance Association estimates that close to two out of every five American women and a smaller number of men dye their hair.

The decision to change hair color has recently become more complicated because some recent studies have linked hair coloring with an increased risk of contracting certain cancers. To make matters more confusing, other studies do not support those findings. Most hair dyes also don't have to go through pre-market testing for safety that other cosmetic color additives do before hitting store shelves. Consumers are often on their own, consequently, when deciding whether hair dyes are safe.

FDA is responsible for overseeing the safety of cosmetics sold in this country and can prohibit the sale of any cosmetics found harmful-- except most hair dyes. Although the adulteration provision of the Food, Drug, and Cosmetic Act enables FDA to seek removal of a cosmetic from the market if it is shown to be harmful under conditions of use, hair colorings made from coal tar were given special exemption from such bans when the act was passed in 1938.

The main ingredient in the coal-tar hair dyes manufactured at the time prompted an allergic reaction in some susceptible individuals. Fearing FDA would ban the sale of the hair dyes because some users might develop a rash or have other allergic reactions, the industry successfully lobbied before the act passed to get coal-tar hair dyes exempted from the adulteration provision. Manufacturers were required, however, to include a warning in the labels that the products can cause skin irritation in certain allergic individuals. Most hair dyes in use today derive their ingredients from petroleum sources, but have been considered coal-tar hair dyes by FDA because they contain some of the same compounds found in these older dyes.

Cancer in Animals

In 1978, FDA proposed to require a warning on the labels of hair dyes containing the compounds 4-methoxy-m-phenylenediamine (4MMPD) or 4-methoxy-m-phenylenediamine sulfate (4MMPD sulfate), two coal-tar ingredients. This followed findings by researchers at the National Cancer Institute in Bethesda, Md., that rodents fed either of the chemicals were more likely to develop cancer than animals not fed the substances.

The researchers put the compounds in the animals' feed rather than on the animals' skin because they were trying to assess the effects of hair dye ingredients inside the body. (Other studies have shown that a small percentage of hair dye is absorbed from the scalp and passed into the bloodstream, where it can travel to other organs and tissues.) To detect a cancer-causing effect of the compounds in a short period in a limited number of animals, researchers fed the animals large doses of the haft dye ingredients.

Some researchers say that extrapolating results from ingested hair dye studies to absorbed hair dye use cannot accurately assess cancer risk because the compounds being tested are altered or are absorbed differently in the gut than they are when applied to the scalp. Moreover, tests of individual hair dye ingredients don't measure the health hazards of the highly reactive compounds that are formed when the various ingredients in a specific hair dye are mixed together and applied to hair.

In other studies, when investigators painted 4MMPD on the skin of rodents, there was no evidence that the compounds caused cancer in the animals. But critics claim that not enough of the chemical penetrates the skin from the small areas on which it's applied to accurately assess the compound's ability to prompt cancers in a limited number of animals.

After FDA adopted the requirement of a warning about 4MMPD and 4MMPD sulfate, manufacturers stopped using the chemicals in their hair dyes. In addition, the hair dye industry has stopped using several other ingredients found to cause cancer in animals. But some of the cancer-causing compounds have been replaced by similarly structured chemicals. However, some scientists feel that the similar structure of these ingredients makes it likely that their cancer-causing potential won't differ much from the chemicals they're replacing. The agency continues to monitor the situation and review studies as they are completed.

Cancer in People

Several studies have tried to pinpoint the risk of various cancers to hair dye users by calculating the difference in frequency of cancer in people who color their hair and those who don't.

Some of these studies found an increased risk of cancer associated with hair dye use, but failed to consider the effects of other cancer-causing agents, such as cigarette smoke, when comparing the two groups. In other studies, the numbers of people included were too small to lend much statistical credence to the findings.