CTPA critically breaks down association between chemical hair straighteners and uterine cancer
31 Oct 2022 --- The Cosmetic, Toiletry and Perfumery Association (CTPA) is challenging the findings of a recent National Cancer Institute (NCI) study on the association between using chemical hair straighteners and uterine cancer. CTPA disagrees and states that “hair straightening products are safe and do not cause cancer.”
“Just like all cosmetics and personal care products, cosmetic hair straighteners must be confirmed safe for us to use before they can be sold. Companies put their ingredients and products through years of development and a legally required in-depth safety assessment, part of which must rule out any risk of the ingredients causing cancer,” comments pharmacist Dr. Emma Meredith, director-general at CTPA.
She further states that companies not only do this because safety is their highest priority, but also because the UK has strict laws dedicated to the safety of cosmetics.
Science-based opinions
CTPA notes that such studies and reports can cause an alarm which is why its scientific team delved into the NCI study in detail. The team concludes that the study does not show that hair straighteners are unsafe or that their ingredients cause cancer.
The scientific team highlights that understanding the relationships between potential risk factors and diseases can be difficult. The NCI study gathers data on participants’ different characteristics and lifestyle factors, which were also associated with a higher risk of uterine cancer.
Several chemicals suggested by the authors as possibly being responsible for a link between these products and cancer are either banned or not used in cosmetics.
The study did not find information on which hair products nor ingredients the women used. Therefore, a link between hair straighteners and cancer cannot be made.
Sister Study in brief
The ‘Sister Study’ by NCI is a US-based research program that enrolled 50,000 women who had at least one sister diagnosed with breast cancer.
Participant characteristics and lifestyle factors were recorded, such as age, ethnicity, education, Body Mass Index, smoking and alcohol status, and how often they used different hair products.
The women were regularly contacted for ten years after enrolling to check up on new cancer diagnoses and other health-related changes.
“Because black women use hair straightening or relaxer products more frequently and tend to initiate use at earlier ages than other races and ethnicities, these findings may be even more relevant for them,” says Dr. Che-Jung Chang, an author of the study.
“More research is needed to confirm these findings in different populations, to determine if hair products contribute to health disparities in uterine cancer, and to identify the specific chemicals that may be increasing the risk of cancers in women,” suggests Dr. Alexandra White, head of the NIEHS Environment and Cancer Epidemiology group and lead author of the study.
CTPA analysis of the study
Upon reading the study, CTPA concludes that “one factor doesn’t necessarily cause another.”
The study authors reported that women diagnosed with uterine cancer were more likely to have used hair straightening products at least once over the past 12 months than the rest of the women in the study.
The authors also found that the women with uterine cancer were likely to be older, less physically active and had a higher BMI than the rest of the participants.
CTPA suggests that the study could have equally linked these other factors to post a higher risk of uterine cancer in its conclusion.
Based on this, CTPA suggests that the study could have equally linked these other factors to post a higher risk of uterine cancer in its conclusion.
Critical thinking
The association highlights that when looking at scientific studies which make an association between two factors, it is vital to consider other factors that may be responsible or contribute to the study result. They stress that the two associated factors do not mean one has caused another.
“For example, the women with uterine cancer were also slightly more likely to have a college degree than the overall study average, but it wouldn’t make sense to suggest that having a college degree has any causative role in uterine cancer,” continues CTPA.
“The suggested reasons for an association between hair straighteners and cancer are unfounded.”
The authors suggest that using hair straighteners and uterine cancer may be related to specific product ingredients. However, the study did not gather data on the products used or their ingredients.
Several chemicals suggested by the authors as possibly being responsible for a link between these products and cancer, i.e., phthalates and bisphenol A, are either banned or not used in cosmetics.
One does not cause another
The study also found that using other hair products, such as dyes, was not associated with higher uterine cancer. Still, these products are likely to contain a similar number of the same “safe” ingredients as straighteners.
Moreover, women who had dyed their hair over the past 12 months were less likely to have uterine cancer than those who had not used hair dyes – illustrating the unreliability of associations between the two factors.
“Additionally, the study suggests that Black women could be affected more by this observed association of hair straightener use, even though the generated data show ‘no differences in the hazard ratios between racial and ethnic groups,’” adds Kimberly Norman, Diplomate American Board of Toxicology, ERT at the Personal Care Products Council, whose response to the NCI study aligns with CTPA.
Safe by law
The association highlights that all cosmetic products sold in the UK are strictly regulated by legislation that aims to protect users’ safety. 
It is vital to consider other factors that may be responsible or contribute to the study result.
All ingredients in cosmetics and personal care products undergo research by industry expert scientists and independent scientists who report to authorities worldwide before the product is available on the market. Additionally, the product must be approved by a safety expert.
Safety assessments factor in the science behind ingredients, product users, how and where they are used and for how long.
Companies also monitor consumer use and reactions to the product and review new research when it becomes available to ensure the safety of their products.
“We can have confidence in the safety of our hair straighteners and all cosmetic products,” concludes CTPA.
Edited by Venya Patel
