Most of the concern about the safety of hair dye centers on the two main parts, the color and the developer. The reaction involves p-phenylenediamine which reacts with hydrogen peroxide to color hair. The darker shades contain more PPD than the lighter shades.
Skin Exposure to PPD
It is clear that PPD sensitizes skin over time. Itching, rash and more severe allergic reactions to PPD are quite well known. Testing on a patch of skin before dyeing hair is a highly recommended routine for users. Allergies can develop over time and testing alerts the user to a reaction before applying larger amounts and risking a larger reaction.
Hair dye is applied at the roots most frequently as users’ hair grows out and the original color reappears. In the course of application, the scalp is in contact with the chemicals. The scalp is densely populated with blood vessels and some of the chemical is absorbed into the body through it.
Likewise, the hands that apply hair dye will encounter some of the chemicals. Frequent appliers of color, such as colorists in salons, will experience the most exposure. Gloves protect the hands, but reusing gloves on multiple applications will expose the wearer to more of the chemicals according to researchers.
Studies Show Some Links to Cancer
European health authorities have banned some of the PPD compounds for suspected risks to humans. The American Cancer Society reports that studies have been either inconclusive or have pointed to a higher risk to the hair dressers who use the dyes almost daily. It is important to note that PPDs are a class of chemicals and some of the members of the class have been banned, but not all.
Though PPD has been shown to cause cancer in laboratory animals, it was fed to them internally in high doses over long periods of time. Animal studies proved that PPD can enter the bloodstream through the skin, but none of the resulting tests linked the exposure through skin to higher risk of cancer.
The main concern with PPD’s and cancer appears to be a slightly higher incidence of bladder cancer. Most studies have not found any link to breast cancer. Most links to cancer in humans have been found to be too weak to point to a major public health risk.
Some in the cosmetic industry argue that the links to increased risk are weak and that laboratory animal research has failed to show any increased risk from skin exposure. Formulations, they say have changed and improved from the products available in the 1980's.
Alternatives and Precautions
Vegetable dyes and traditional henna dyes are perhaps safer, but modern versions often have many of the same chemical components as the synthetic dyes, just in lower concentrations. The natural dyes do not last as long, requiring more frequent application. They also tend to be more expensive.
Most experts say caution is always the wise response. The Food and Drug Administration has published some advice for users of hair dyes on their website. It recommends following the directions exactly and proper precautions to minimize contact. Wear gloves and rinse the scalp thoroughly to minimize contact with skin.
Resources:
- American Cancer Society
- Annals of Occupational Hygiene
- Cosmetic Ingredient Review
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