Hair coloring (HC) is a beauty practice that changes one’s natural hair colour using chemicals to remove pigments in the hair shaft, melanin, by oxidizing the pigments, and replacing them with other pigments of choice. HC comes in different types, depending on how long a person wants the colour to last by changing the concentration of hydrogen peroxide (HP), ammonia, and paraphenylenediamine (PPD). Ammonia causes the swelling of the hair shaft, opening hair cuticles so HC pigments can penetrate into hair. HP oxidizes melanin in the hair strand, removing its natural colour to create a canvas. Finally, PPD complexes with HP to form a colourful complex, which then binds to our hair to give it a new colour.
Health concerns relating to hair colouring practice.
It is undeniable that HC improves the appearance drastically if you choose the right colour, but the harm of “forcing” hair to change color to health is extremely harmful that not many people are aware of. Several studies reported a possible correlation between certain chemicals in many oxidative-type HC products to a few sub-categories of cancer. Ames et. al. founded that the oxidation reaction between HP and each of the three main chemicals in oxidative-type hair colouring products – PPD, 2,5-diaminotuluene (TDA), and 2,5-diaminoanisole – yield a mutagen Bandrowski’s base. They conducted a facial absorption test on rats and found that this compound is a carcinogen to rats. Some HC users reported experiencing allergic reactions after using an at-home HC product or obtaining HC services from salons. Several hairdressers experienced frequent incidents of hand dermatitis from long-term exposure to HC products. This is because PPD, TDA, and other chemical compounds in many HC products are strong and extreme sensitizing compounds that lead to contact dermatitis (Figure 1) in many people who directly come in contact with the chemicals.
Figure 1: Contact dermatitis occurs when skin comes into contact with a substance that causes our body to elicit one or several allergic reactions. Source: Wikimedia
Why do people still choose to dye their hair?
Despite health concerns surrounding chemical compounds in HC products, HC remains a popular beauty practice these days among all ages, either to change their natural hair colours or to cover up grey hairs. For many people, HC not only improves their appearance and boosts their self-confidence if they choose a colour that matches their complexion but also a way to express their personality. To avoid the harmful effects that come from strong concentrations of HP and other compounds in HC products, experts from the US Food and Drug Administration recommend people to opt for temporary or semi-permanent HC, which contains the same chemical formula in permanent HC products, but at lower concentration. In addition, hairdressers always wear gloves, and some would wear masks to avoid inhaling the fume, while handling HC products. However, HC users and hairdressers should consult dermatologists or health experts if they experience any reactions or health concerns after using HC products to avoid the risk of having cancer.