Wednesday, May 12, 2021

Do hair dyes increase the risk of cancer? – Harvard Health Blog

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Personal use of hair dye is very common, with estimates that 50% or more of women and 10% of men over 40 color their hair. However, with social distancing guidelines in place amid the ongoing pandemic, many people have given up on their regular barber appointments. As natural hair colors fade, let’s get to a layered question: Does permanent hair dye increase cancer risk?

Decades of research, conflicting results

Hair dyes come in three main varieties: oxidative (permanent), direct (semi-permanent or temporary) and natural dyes. Most hair dyes used in the United States and Europe – both do-it-yourself and salon dyes – are permanent dyes. They undergo chemical reactions to create pigments which are deposited on the hair shafts and may present the greatest risk of cancer.

People are exposed to the chemicals in hair dye through direct contact with the skin or by inhaling fumes during the coloring process. Occupational exposure to hair dye, as experienced by hairdressers, has been classified as likely carcinogenic. However, it remains unclear whether staff using permanent hair dye increases the risk of cancer or cancer death.

Many studies have explored the relationship between the use of personal hair dye and the risk of cancer or cancer-related death. Contradictory conclusions resulted from imperfect studies due to small study populations, short follow-up times, inadequate classification of exposures (personal or occupational) or type of hair dye (permanent or non-permanent), and incomplete accounting of risk factors specific to cancer beyond permanent hair dye use.

Permanent hair dye does not appear to increase overall cancer risk, recent study finds

In a recent study in BMJ, researchers at Harvard Medical School evaluated the use of personal hair dye and the risk of cancer and cancer-related death. The study authors analyzed survey data from 117,200 women enrolled in the Nursing Health Study, collected over 36 years from 1976. They compiled information that included age, race, body mass index, smoking, alcohol consumption, natural hair color, use of permanent hair dye (never user vs never user, age at first use, duration of use, frequency of use) and risk factors for specific types of cancer.

Compared to non-hair dye users, participants who had previously used permanent hair dyes did not have an overall higher risk of cancer or cancer-related death.

Among specific cancers, the risk of basal cell carcinoma was slightly higher (the type of skin cancer) among permanent users versus non-users. The risk of some breast and ovarian cancers appears to increase with long-term use of permanent dye. Women with naturally dark hair appeared to have an increased risk for Hodgkin lymphoma, and women with naturally light hair had a higher risk of basal cell carcinoma.

The authors were cautious in reporting their findings, concluding that further investigation is needed to better understand the associations identified. In addition, we must keep in mind that the association does not prove causation.

A well-designed study also had certain limitations

This was a large, well-designed study with high response rates from participants. The researchers analyzed detailed data, which allowed them to determine to what extent the risk of cancer was attributable to personal use of permanent hair dye rather than to other potential risk factors.

This study also had several limitations. First, the participants were nurses of predominantly European origin, which means that the results are not necessarily generalizable to men or to other racial or ethnic groups. Second, the study could not report on every cancer risk factor (for example, exposure to pesticides and other environmental chemicals). Data was not collected on hair care products other than hair dyes, and subjects may have mistakenly reported the use of permanent hair dyes when they were actually using semi-permanent or natural dyes. . Without data on the actual color of the hair dyes used, the authors assumed that the color of the hair dyes correlated with the natural shades of the hair. This assumption can miscalculate true chemical exposures, as in the case of dark haired users who have experienced additional chemical exposures by stripping the darker natural pigment.

To dye or not to dye?

Once pandemic restrictions are lifted, some may reconsider whether to dye their hair. The highlights of this study are:

  • Personal use of permanent hair dye did not increase the risk of most cancers or cancer-related deaths. It is reassuring, but continuous safety monitoring is necessary.
  • More research is needed to study various racial and ethnic origins, specific hair dye colors (light vs. dark), cancer subtypes, and exposure levels (personal or professional).
  • Although this study found possible associations between the use of permanent hair dyes and an increased risk of certain cancers, there is not enough new evidence to move the needle on recommendations for personal use of dyes. permanent capillaries. Until you know more, consider your personal and family history when deciding to use permanent hair dyes. If in doubt, consult your doctor for further advice.

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