Types of Hair Dyes

Hair dyes vary greatly in their chemical make-up. People are exposed to the chemicals through skin contact. There are 3 main types of hair dye:

Temporary hair dyes

• cover the surface of the hair but do not penetrate into the hair shaft 
• last for 1 to 2 washings

Semi-permanent hair dyes

• do penetrate into the hair shaft 
• typically last for 5 to 10 washings

Permanent hair dyes (two different kinds)

• cause lasting chemical changes in the hair shaft 
• are the most popular types of hair dyes, because the color changes last until the hair is replaced by new growth.

Oxidative hair dyes contain colored dye substances (such as p-phenylenediamine or 2-nitro-p-phenylenediamine) and hydrogen peroxide. These substances go through a chemical reaction inside the hair to become a dye. Oxidative hair dyes are mixed just before they are used.

Progressive hair dyes contain metal salts (such as lead acetate or bismuth citrate) as their active ingredients. They gradually change hair color by reacting with sulfur in the hair.

Concern about cancer risk is largely limited to the semi-permanent dyes and the oxidative type of permanent dyes. Because dark brown and black dyes have higher concentrations of suspected cancer-causing substances (carcinogens), these products are of greatest potential concern.

Does Hair Dye Cause Cancer?

Two kinds of evidence tell us about the potential cancer risk of hair dyes -- epidemiologic studies and laboratory studies. Epidemiologic studies in humans give us information about the possible causes of disease, occurrence of disease in a population or its subgroups, and trends in the frequency of disease over time. Laboratory studies are most often done on animals.

What Do the Experts Say?

Based on animal and human evidence, expert agencies have looked at the possibility of hair dyes causing cancer.

The International Agency for Research on Cancer (IARC) evaluates exposures that may be carcinogenic. IARC classifies exposures into one of 4 categories:

• Group 1 exposures are those "known to be carcinogenic to humans," usually based on "sufficient" human evidence, but sometimes based on "sufficient" evidence in experimental animals and "strong" human evidence. 
• Group 2 exposures are divided into 2 categories. Group 2A ("probably carcinogenic to humans") has stronger evidence, and Group 2B ("possibly carcinogenic to humans") has weaker evidence. 
• Group 3 exposures are not considered classifiable because the available evidence is limited or inadequate. 
• Group 4 exposures are "probably not carcinogenic to humans" based on evidence suggesting these substances do not cause cancer in humans or in experimental animals.

The IARC concluded in 1993, that the hairdressers and barbers probably are exposed to cancer causing substances (Group 2A), but that the evidence of increased cancer risk was limited. There was not enough evidence at that time for the IARC to evaluate the possible cancer-causing risks of personal use of hair dyes.

Since this IARC decision in 1993, many more studies have been done worldwide.

What Do the Studies Suggest?

Studies have looked at whether people who use hair dye products or people who regularly work with them have an increased risk of bladder cancer, leukemia, multiple myeloma, Hodgkin disease, non-Hodgkin lymphoma, lung cancer, breast cancer, oral cancer, and cervical cancer. The evidence from these studies remains quite inconsistent. Most of the available evidence does not support a link to cancer risk. Those studies that do show a link find that it is too weak to be considered a major public health concern.

Studies such as these need to be repeated in larger groups of people so that experts can get a better look at possible problems linked to hair dye use.

What Do Animal and Laboratory Studies Suggest?

Some of the ingredients (such as 4-methoxy-m-phenylenediamine or 4-MMPD, 4-MMPD sulfate, 4-chloro-m- phenylenediamine, 2,4-toluenediamine, 2-nitro-p- phenylenediamine, 4-amino-2-nitrophenol, C.I. Acid Orange 3 and C.I. Disperse Blue 1) in hair dyes have been shown to cause cancer in laboratory animals. In these studies, however, animals were fed large amounts of the dyes over a long period of time. Although studies have shown that some of the dye applied to an animal's skin is absorbed into the bloodstream, most have not found any association between skin application and cancer risk.

Does Hair Dye Cause Any Other Health Problems?

Some of the ingredients in hair dyes can cause allergic reactions leading to severe skin and eye irritation. Eye irritation can seriously affect vision and, very rarely, lead to blindness. For these reasons, it is recommended that users test these products on a small area of skin before using them on their hair and scalp. It is also for these reasons that these products should not be used to dye eyebrows.

What Should I Do If I Have Been Exposed to Hair Dye?

There are no current recommendations for special testing to look at exposure to hair dye ingredients. Other than recommendations that apply to everyone (having routine screening exams, eating a healthy diet, being physically active, etc.) no specific medical advice is needed for current or former hair dye users.

What's the Bottom Line?

Most of the available evidence does not show hair dyes to be a significant cancer risk factor. However, the findings of published studies remain inconsistent. The US Food and Drug Administration (FDA) provides some suggestions for people worried about hair dyes as a cancer risk factor (FDA, 1993), (FDA, 1997):

• Don't leave the dye on your head any longer than necessary. 
• Rinse your scalp thoroughly with water after use. 
• Wear gloves when using hair dye. 
• Carefully follow the directions in the hair dye package. 
• Never mix different hair dye products, because you may cause potentially harmful reactions. 
• Be sure to do a patch test for allergic reactions before putting the dye in your hair. Do a patch test before every use. 
• Never dye your eyebrows or eyelashes. 
• Delay dyeing hair until later in life when it starts to turn gray. 
• Consider using henna, which is largely plant-based, or hair dyes that are lead acetate-based.

References

Altekruse SF, Henley SJ, Thun, MJ. Deaths from hematopoietic and other cancers in relation to permanent hair dye use in a large prospective cohort study. Cancer Causes and Control 1999; 10:617-625.

Cook LS, et al. Hair products use and risk of breast cancer among young women. Cancer Causes and Control 1999; 10:551-559.

Correa, A, et al. Use of hair dyes, hematopoietic neoplasms, and lymphomas a literature review. II Lymphomas and multiple myeloma. Cancer Investigation 2000; 18:467-479.

Correa, A, et al. Use of hair dyes, hematopoietic neoplasms, and lymphomas a literature review. II Leukemias and myelodysplastic syndromes. Cancer Investigation 2000; 18:366-380.

Gago-Dominguez M, et al. Use of permanent hair dyes and bladder cancer risk. Intl J Cancer 2001; 91:575-579.

Grodstein F, et al. A prospective study of permanent hair dye use and hematopoietic cancer. J Natl Cancer Inst 1994; 86:1466-1470.

Holly EA, Lele C, Bracci PM. Hair color products and risk for non-Hodgkin’s lymphoma: a population-based study in the San Francisco bay area. Amer J Public Health 1998; 88:1767-1773.

Lavecchia C, Tavani A. Epidemiological evidence on hair dyes and the risk of cancer in humans. Eur J Cancer Prevention 1995; 4:31-43.

Rollinson DE, Helzlsouer KJ, Pinney SM. Personal Hair Dye Use and Cancer: A Systematic Literature review and Evaluation of Exposure Assessment in Studies Published Since 1992. Journal of Toxicology and Environmental Health, Part B 2006; 9:413-439.

Takkouche B, Etminan M, Montes-Martinez A. Personal Use of Hair Dyes and Risk of Cancer: A Meta-analysis. JAMA 2005;293(20):2516-2525.

US Food and Drug Administration. Hair dye products. November 1997. Available at: http://www.cfsan.fda.gov/~dms/cos-hdye.html. Accessed May 9, 2007.

US Food and Drug Administration. Hair dye dilemmas. 1993. Available at: http://vm.cfsan.fda.gov/. Accessed June 30, 2007.

Revised: 06/30/2007