Hair Relaxers, Black Women & Uterine Cancer – The Truth Behind the Study’s
- Admin
- Nov 4
- 6 min read
Updated: Nov 4
Everybody online is saying “relaxers cause cancer” — but that’s not the full story.
In this video, Cyn Doll breaks down the real science behind chemical hair straighteners, Black women’s health, and the uterine cancer study that’s all over the internet.
Over 44,000 women were followed for 22 years, and only 347 were diagnosed — less than 1%. So why is the internet acting like every relaxer is a death sentence?
Let’s talk about what the study actually said, what it didn’t test, and how things like diet, estrogen balance, vitamin D, and lifestyle might be part of the bigger picture.
💅🏾 This video covers:
The truth about the Black Women’s Health Study and what they really found
How diet, environment, and hormones affect uterine cancer risk
Why correlation isn’t causation (and what that means for your hair routine)
How to make safer, smarter decisions with relaxed or natural hair
✅ What the major studies
did
measure
The 2022 large study by National Institute of Environmental Health Sciences (NIH/NIEHS) followed ~33,000 U.S. women who reported using chemical hair straightening products (which include relaxers/straighteners).
That study found that women who used straightening products more than 4 times in the previous year had over 2× the risk of uterine cancer compared with women who didn’t.
Another study (in the Black Women’s Health Study) followed ~44,800 Black women for up to 22 years, and found among post-menopausal women that long-term or frequent use of chemical hair relaxers was associated with increased uterine cancer risk (hazard ratios ~1.60-1.70 for heavier use).
Both of these studies mention that the association is with “chemical hair straightening products” (often described as straighteners or relaxers) but they did not collect detailed ingredient lists of the products used. For example, the NIH/NIEHS-led study states: “the researchers did not collect information on brands or ingredients in the hair products the women used.”
🚫 What the studies
did not
specifically show (and what the confusion is about)
Neither study specifically broke down risk by “lye” (sodium hydroxide) vs “no-lye” (e.g., guanidine, ammonium thioglycolate) relaxer formulas. I didn’t find credible evidence in those main publications that they isolated “lye vs non-lye” as a subgroup breakdown.
The studies talk about “chemical hair straightening/relaxing products” in broad terms. They flag chemicals like parabens, bisphenol A, formaldehyde, metals, etc, as possible culprits.
Because ingredient-data are missing, we can’t say from those studies “the lye formula specifically caused the higher risk” or “only non-lye formulas are safe.” The data just don’t allow that claim.
Some of the spread in social media is incorrectly saying “lye relaxers were excluded from the risk study so only keratin/straightening treatments matter.” While I didn’t find a statement that explicitly excludes “lye” formulas, the big missing ingredient-info means we don’t know.
Also, the term “keratin treatments” may be conflated with straighteners/relaxers, but those often have different chemical mechanisms (some release formaldehyde when heated, etc). The studies refer to “chemical straighteners/relaxers/straightening products” rather than specifically “keratin treatments.”
🎯 My verdict (for your site/conversion content)
It’s accurate to say: “Studies show an association between frequent use of chemical hair straightening/relaxing products and increased uterine cancer risk.”
It’s less accurate to say: “The study proved that lye formulas are safe or that non-lye formulas are the only ones risk carries.” That goes beyond the data.
So for conversion/content: emphasize what the studies actually show, mention the gaps (ingredients not captured, lye vs non-lye unclear) and position your advice around reducing exposure and making informed choices—not fear for fear’s sake.
Here’s exactly what they were missing or limited on, straight from the study design and its discussion section:
🧴 1.
No ingredient-level data
They did not collect ingredient information or brand names of the relaxers/straighteners women used.
So they couldn’t tell:
Whether the products were lye (sodium hydroxide) or no-lye (guanidine carbonate, calcium hydroxide, etc.)
Whether they contained formaldehyde, parabens, phthalates, bisphenol A, or other endocrine-disrupting preservatives
If the exposure changed over time (brands reformulate constantly)
💬 Why it matters: Without ingredient lists, the study can’t identify which specific chemical exposures (e.g., lye vs. non-lye vs. keratin formaldehyde systems) are driving the risk — only that “chemical straightener use” overall correlates with uterine cancer risk.
⏱️ 2.
Self-reported use patterns
Participants self-reported their use of relaxers over time — things like:
How often they used them (years of use, frequency)
When they started (childhood, adulthood)
Whether they used it in the last 12 months
💬 Why it matters: Self-reports are subject to recall bias — some participants may misremember their usage frequency or timing, especially over 20+ years.
🩸 3.
No biomarker confirmation
They didn’t collect biological samples to measure exposure (like testing blood, urine, or hair for parabens or phthalates).
💬 So: They couldn’t verify how much of the chemicals actually entered the body — they inferred exposure from usage patterns.
⚗️ 4.
Grouped “relaxers” broadly
The survey question didn’t distinguish between:
“Traditional relaxers” (lye/no-lye)
“Keratin” or “Brazilian blowout”–type treatments
“Thermal reconditioning” systems
💬 Effect: All were lumped under “chemical straighteners,” so the mechanism of action (alkaline bond-breaking vs. heat-activated formaldehyde systems) wasn’t separated.
👩🏾🦱 5.
No direct scalp injury or burn data
The BWHS acknowledged that burns or lesions could enhance absorption of chemicals, but they didn’t collect detailed info on how often participants experienced scalp burns or irritation.
💬 That’s important because frequent burns = more chemical absorption → higher theoretical risk.
🧬 6.
Limited control for co-exposures
They did adjust for lifestyle, BMI, parity, and other risk factors, but they couldn’t fully control for:
Other personal-care product exposures (lotions, fragrances, etc.)
Environmental toxins
Medical conditions or hormone therapy history beyond what was reported
📊 7.
Small number of uterine cancer cases
Even over 22 years, only 347 women developed uterine cancer. That’s enough to detect an association, but not to confidently break it down by every subgroup (like lye vs. no-lye, or childhood start vs. adult start).
🧠 the missing puzzle pieces
Category
What They Collected
What They Didn’t
Product use
Yes (frequency, duration, age started)
No brand or ingredient info (lye/no-lye/formaldehyde/etc.)
Biological exposure
No
No chemical biomarkers
Hair treatment type
All grouped as “chemical straighteners”
Couldn’t isolate keratin vs. relaxer
Scalp health
No
Didn’t track burns or sores
Outcome verification
Yes (medical records)
—
Cancer risk factors
Yes (BMI, hormones, etc.)
Not all lifestyle/environmental co-exposures
So when you hear people say “they didn’t even study lye,” what’s actually true is:
They didn’t collect product-level ingredient data — so they can’t confirm or exclude lye formulas, keratin treatments, or anything else individually.
💬
“Let’s be real for a sec…”
Everybody online yelling “relaxers cause cancer,” but nobody’s talking about how the same women in those studies were eating what them old magazine recipes told us to cook back then 😭
Those studies followed Black women from the ‘90s — Essence readers, remember? We was frying everything in Crisco, heavy on the sauces, light on the veggies, and hitting the salon every few weeks. That’s lifestyle, not just hair.
Yeah, scientists found a link between chemical straighteners and uterine cancer… but a link don’t mean it’s the cause.
They didn’t test the products, they didn’t test the women’s blood — just surveys.
And if your diet’s full of estrogen-boosting foods, low vitamin D, plus everyday exposure from plastics, perfumes, and cooking oils? Baby, that’s a whole mix of things feeding the same issue.
So nah — it ain’t fair to dump it all on relaxers.
It’s bigger than that.
It’s diet, environment, ingredients, and habits.
Until they test it for real, all we can do is stay informed, eat cleaner, read our labels, and protect our scalp.
That’s how we move smart — not scared 💅🏾
📚
Sources & Studies Mentioned
(Click the links to read or verify the data yourself 👇🏾)
1️⃣ Chang et al., 2022 – NIH / Journal of the National Cancer Institute
Hair straightening chemicals and uterine cancer risk (Sister Study)
2️⃣ Bertrand et al., 2023 – Environmental Research (Black Women’s Health Study)
Hair relaxer use and uterine cancer among 44,000 Black women
3️⃣ Bailey et al., 2025 – National Library of Medicine / PMC
Hair straighteners, relaxers, and risks of uterine, breast, and ovarian cancer
4️⃣ Wise et al., 2012 – American Journal of Epidemiology
Hair relaxer use and risk of uterine fibroids in African-American women
5️⃣ Eberle et al., 2019 – International Journal of Cancer
Hair dye and chemical straightener use linked to breast cancer risk
6️⃣ James-Todd et al., 2021 – Environmental Research
Hormonal activity in commonly used Black hair care products
7️⃣ Preston et al., 2021 – Environmental Health
Endocrine-disrupting chemicals and hair product use among Black women
8️⃣ Schildroth et al., 2024 – Chemosphere Journal
Hair product use and urinary biomarkers of endocrine disruptors in Black women
9️⃣ NIEHS (National Institute of Environmental Health Sciences) Summary
Straighteners, EDCs, and women’s health – overview of ongoing studies
10️⃣ FDA Formaldehyde Update (2024)
Proposed rule to ban formaldehyde in hair straightening products
💬
Copy-ready line for your box:
🧠 Verified sources from the NIH, PubMed, Environmental Research, and the Black Women’s Health Study. Always do your own reading before you let the internet scare you 💅🏾
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