Hair relaxers tested by UCT lab found to be corrosive to skin

09 March 2020 | Story Nobhongo Gxolo. Photo Pexels. Read time 10 min.
A study by UCT scientists found that commercially sold hair relaxers tested were corrosive to skin.
A study by UCT scientists found that commercially sold hair relaxers tested were corrosive to skin.

Scientists from the Hair and Skin Research (HSR) Laboratory at the University of Cape Town (UCT) have published a study in the South African Medical Journal. According to the paper, all commercially sold hair relaxers they tested, including those advertised for children, were found to be at pH levels that are corrosive to skin.

An estimated seven out of every 10 women of “black African ancestry” use hair relaxers. Global and local occupational health and safety guidelines have determined a pH greater than 10.5 as an irritant, and one greater than 11.5 as corrosive to skin. All 121 tested relaxers (including 54% that were international brands) had a pH greater than 11.5.

The researchers purchased relaxers from various retailers in Cape Town. This locale was acknowledged as a limitation of the study. Still, the shops in the city – most of which are found around the country – offered a good cross-section of the available products.

Ntombenhle Sishi, a cosmetic formulations scientist and co-author on the paper, explained, “Every cosmetic product lists ingredients. We classified the relaxers according to the three chemical actives: sodium hydroxide, calcium hydroxide and lithium hydroxide. Of the 121 products, 76 fell under the sodium hydroxide category, 24 were calcium hydroxide and 21 were lithium hydroxide.”


“Relaxing hair over time can leave the hair follicles completely damaged because the compounds used cause inflammation of the scalp.”

Most consumers and hairdressers often mention that no-lye kits, with calcium hydroxide as the main active ingredient, and those produced for children, are safer than sodium-based relaxers.

“One such product is a relaxer with an activator that must be mixed into it. It was packaged with a conditioner, which is usually meant to protect the hair and scalp. We wanted to simulate real-life conditions according to the manufacturer’s instructions, yet we found that the maximum pH was 13.8 – almost 14. Worryingly, this was meant to be used on children,” said Sishi.

“The skin of a child is not yet fully developed, and so should not be exposed to such a high pH. Not that adult skin should be either.”

The researchers found that six of the 76, four of the 24 and eight of the 21 relaxers were targeted at children. Sishi referenced a study that Professor Nonhlanhla Khumalo, senior author and head of the Division of Dermatology in the Department of Medicine, ran in 2007. Here she found that four out of five school children relaxed their hair.

Sishi explained: “Hair loss doesn’t happen overnight; it builds over time. The reality is that 8.6% of children entering the school system in Grade 1 show signs of hair alopecia. By the time they get to matric, that number has almost tripled – at 21.7%. Relaxing hair over time can leave the hair follicles completely damaged because the compounds used cause inflammation of the scalp. Continuous use of relaxers exacerbates this damage.”

A brief history lesson

Garret Morgan, a descendant of slaves who received little education but had an incredible talent for innovation, lived in Cincinnati. He was 32 when he stumbled on the hair-straightening prototype that would result in a patent. Morgan had a tailor shop in 1909 and, wanting to reduce friction in his sewing machines, he tried a concoction that contained sodium hydroxide. He wiped his hands on a furry cloth and after noticing a change in texture tried the product on a neighbour’s dog – Airedales have notably curly fur. Applying the cream resulted in the dog’s fur straightening, prompting Morgan to try it out on his own hair. It worked and he later founded the G.A. Morgan Hair Refining Company.

“The first relaxer patent was issued in 1913. It’s been more than 100 years since and we are still using sodium hydroxide and similar molecules,” Sishi said.

She also noted that women have been relaxing hair for a long time, regardless of warnings. Dermatologists like Khumalo have been publishing various studies that show a strong link between relaxers and hair damage, breakage and various types of alopecia. The HSR Lab was started by Khumalo partly to train scientists to produce safe cosmetics – through the first graduate Advanced Diploma in Cosmetic Formulation Science in Africa. The lab also aims to offer the country a facility for testing illegal and toxic ingredients in cosmetics – and so to protect the public from harm.

Healthier alternatives

Sishi said the responsibility should lie with the hair industry, the manufacturers and formulators like herself to “think out of the box and create safer alternatives for the people who want to straighten their hair”.

The hair industry narrative focuses on marketing relaxers as more cost-effective than alternative products. The narrative speaks to making kinky, curly or coiled hair more manageable. But hair care alternatives, including the importance of moisture in making hair more manageable, exist.


“Relaxers should not be an option; they are toxic and don’t belong on anyone’s skin.”

The natural hair movement has evolved to include vloggers, bloggers and influencers seeking to educate and share tips encouraging healthy hair management. Support groups and communities for like-minded people exist online on social media pages. Documentaries, like comedian Chris Rock’s Good Hair, which look at politics and culture as factors driving the industry’s economy, have received critical acclaim. Celebrities like Tracee Ellis Ross and Taraji P Henson – icons in the film industry – have developed their own hair care ranges. The rhetoric remains the same: relaxers aren’t the only option.

“Relaxers should not be an option; they are toxic and don’t belong on anyone’s skin," said Sishi.

The South Africa Hair Care Market – Growth, Trends and Forecast (2020─2025) report put the local hair care market revenue at US$116.46 million in 2018. This translates to R1.7 billion.

“Sodium hydroxide is such a cheap chemical; it gives manufacturers a huge profit margin. You can’t make money while causing damage,” she added.

Her position, as a leading woman in science based at the top university on the continent, allows her to take the industry in her hands and supply it with “cosmetic scientists who’ve been trained with an overarching message of safety. You can’t be damaging and beautifying – it’s an oxymoron. The cosmetic scientists are encouraged to go out there and not do harm.”

A call to stop relaxing

The prevalence of traction alopecia (hair loss caused by tightly pulled hairstyles) in African natural hair sits at 21%. Plaiting increases that number to 33%. Relaxing moves the needle by a further 2%. Introducing weaves to already relaxed hair increases that to 48%. Effectively, one in two women risk developing traction alopecia when they braid or weave relaxed hair. Although Sishi conceded that many people want to straighten their hair, she said that they should “stop using relaxers”.

Sishi added, “I believe scientists, based on their unique vantage point, have a duty to improve the public’s quality of life and publicise these types of results so that people can make informed choices about what they put on their children’s and their own skins – especially when it comes to the products that they use daily.”

She said it’s pointless to do science just for the sake of it – “science must be done to impact the community”.


“As an African woman scientist I am sitting at a vantage point where I can research and inform.”

On Sunday, 8 March, International Women’s Day commemorated working women – the team behind this paper embodies this. The responsibility of those who hold knowledge is to inform.

“As an African woman scientist I am sitting at a vantage point where I can research and inform … and use science to the benefit of those who do not have this positioning. We address issues no one is attending to. And in this case, doing so has the potential to encourage manufacturers to think out of the box – this is the second aim.”

Sishi mentioned that the third function of the research was to address their concern about the chemicals being allowed into the market by the current regulations.

“Can the status of relaxers be reviewed – and so moved from being allowed with restrictions to being banned completely?”

Fortunately, more people are opting for the natural route. This encourages an increase in the availability of alternative options as more products are being tested and marketed.

“Before relaxers there were African hair care options. Zozibini [Tunzi], Miss Universe, is an example of someone who is redefining beauty standards and proving that you can be yourself, be authentic, and be appreciated and accepted with your natural hair.”

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