The short answer
A large NIH study found that women who frequently used chemical hair straighteners or relaxers had a higher risk of uterine cancer than those who did not. This is an observed association, not proof that the products cause cancer, and the overall risk remained low. Research is ongoing, and frequent users may reasonably choose to cut back.
A large NIH study linked frequent relaxer use to higher uterine cancer risk.
This is an observed association, not proof of cause and effect.
The overall risk of uterine cancer still remained low.
Frequent use — not occasional use — was the pattern studied.
Choose how you want to understand this
The full explanation.
The claim
News reports and lawsuits have highlighted claims that chemical hair straighteners and relaxers cause cancer, especially uterine cancer. The attention grew after a large U.S. government study reported a link, and the concern falls hardest on Black women, who use these products more often.
What the study found
In the NIH-funded Sister Study, women who reported frequently using chemical hair straighteners or relaxers (more than about four times in the past year) had roughly double the rate of uterine cancer compared with women who did not use them. Because uterine cancer is relatively uncommon, even a doubled rate meant the estimated risk rose from a low baseline to a still-modest level.
What it does and does not prove
This kind of study can show an association but cannot by itself prove the products cause cancer — other differences between users and non-users could play a part. Researchers have pointed to chemicals in some products, such as certain preservatives and endocrine-disrupting compounds, as biologically plausible, but more research is underway. Some studies have also examined possible links to other cancers.
The bottom line
Frequent use of chemical hair straighteners is associated with a higher uterine cancer risk in a large, credible study, though this is not yet proof of cause and the overall risk stays low. People who use these products often — and want to be cautious while research continues — may reasonably choose to cut back or space out treatments. Unusual bleeding or other new symptoms are always worth discussing with a clinician.
Words to know
Tap any term to see what it means.
Common questions
▸Do hair relaxers cause cancer?
A large study links frequent use to higher uterine cancer risk, but this is an association, not proof of cause and effect. The overall risk remained low.
▸How much use did the study look at?
The higher risk was seen in women who used these products frequently — more than about four times in the past year — not occasional users.
▸Should I stop using relaxers?
That is a personal choice. Some frequent users may prefer to cut back or space out treatments while research continues.
▸Who is most affected by this concern?
Black women use these products more often, so the concern falls hardest on them, which makes the research especially important.
Questions to ask your doctor
Being prepared helps you get the most out of your appointments. Save or print these questions.
Tap a question to save it to your list (kept on this device).
Your next step
What the evidence shows about common cancer claims.
Test your knowledge
0 of 3 answered
This quiz checks understanding of educational content only. It is not medical advice. Open this quiz on its own page.
How this page was created
Cancer Explained uses AI to organize and translate information from the authoritative sources cited on each page. Automated checks review claims, citations, clarity, duplication, and potential safety concerns before publication. Our content is not currently reviewed by physicians unless a specific qualified reviewer is named on the page. Cancer Explained provides general education and should not replace advice from your healthcare team.
Editorial status: Editorial review complete — This page completed Cancer Explained's editorial checks (sources, safety, plain language, duplication). It has not been reviewed by a physician or other healthcare professional.
Human medical review: not completed. At this time, most Cancer Explained content has not been reviewed by a physician or other healthcare professional. Pages with documented human medical review identify the reviewer, credentials, and review date directly.
Read more about our editorial process, our use of AI, and our corrections policy.
Spotted a problem? Report an error — a factual mistake, broken or outdated source, confusing wording, or anything that seems unsafe. Please do not include names, medical record numbers, dates of birth, addresses, or other identifying medical information in your report.
After using this page, do you understand what to do next?
Anonymous — we only record the answer, never who gave it.