Straighteners, chemical straighteners and treatments for straight and always perfect hair: many people use them regularly, even several times a month. But these beauty tools may have a dark side. The alleged danger is highlighted by a recent study, conducted on a large group of women – which suggests an increased risk of some tumors – including pancreas and thyroid, for those who regularly use these products.
But how much is there to be alarmed about? Let’s try to understand better.
The study
The research followed more than 46,000 women aged between 35 and 74, all without any form of cancer at the start of follow-up, but with a sister who had been diagnosed with breast cancer. Participants provided detailed information on their lifestyle, family history and use of straighteners or chemical straightening treatments in the past 12 months.
The use of straighteners and straightening products was much more frequent in some communities: about two-thirds of black women and a quarter of Hispanic/Latina women used them regularly, while among non-Hispanic white women the use was very limited, just 1-2%. This distribution made it possible to analyze how the use of straightening treatments could influence the risk of tumors in different demographic groups, highlighting possible differences linked to cultural factors and aesthetic habits.
During approximately 13 years of observation, the researchers recorded cases of incident tumors, confirmed when possible through medical reports.
The results? Those who regularly used straighteners or straightening treatments had a significantly greater risk of pancreatic cancer and thyroid cancer than those who did not use them. Non-Hodgkin’s lymphoma was also more frequent among regular users, while for kidney cancer the data was less clear, signaling a possible increase but with evidence that was still imprecise.
In cases of habitual use, defined as more than four treatments a year, the risk of pancreatic cancer more than doubled. These results confirm and expand previous signals that had linked straightening treatments to an increased risk of some tumors, suggesting that the effects could also affect other organs in addition to those already known.
Because the plates could favor the appearance of tumors
The main risk does not come from the straightener itself, but from the chemicals used to straighten the hair. Chemical treatments such as keratin straighteners often contain potentially harmful substances, including formaldehyde, which can release as a gas when treated hair is heated with straighteners or brushes.
It should be noted that, in Europe, free formaldehyde is prohibited in cosmetics; however, some products contain compounds that can release it upon contact with heat.
In addition to formaldehyde, straighteners may contain parabens, phthalates, bisphenol A and heavy metals – substances known to interfere with the endocrine system – which can penetrate through the scalp or be inhaled during use, accumulating over time and creating an environment conducive to cellular damage and genetic alterations.
Repeated exposure to these vapours, especially in closed and poorly ventilated environments, can irritate the eyes and respiratory tract and, according to scientific evidence, cause damage to cells through DNA alterations, oxidative stress and inflammation, all processes that can contribute to the development of tumors.
In essence, it is the interaction between chemicals and heat that generates potentially carcinogenic vapors: using only the straightener or brush without applying chemicals does not pose the same risk.
The limits of the research
It is essential to underline that the study has limitations. Use of treatments was self-reported, therefore subject to recall errors or underreporting. Not all tumors were confirmed by medical reports, and not all confounding factors – such as other chemical exposures or lifestyle habits – may have been accounted for. Furthermore, the relationship between frequency of use and risk is not always linear and some evidence remains “imprecise”. In other words, we cannot say with certainty that straighteners combined with straighteners cause tumors, but the signals that have emerged deserve due attention.
While we wait for more clarity on the issue, experts recommend reducing the frequency of chemical treatments, choosing products that do not contain formaldehyde releases and always ensuring good ventilation during use. Avoiding repeated exposure to chemical vapors, especially indoors, is a simple but effective precaution that we can all put into practice.
