HomeThe science of cosmeticsHow do hair products work?How do I stay safe when dyeing my hair?

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What is the difference between a hair dye and a hair colorant? The terms can be confusing!

Hair colorants contain a mixture of substances called hair dyes, along with other ingredients, to produce dramatic colours and effects to our hair. The actual cosmetic product you use is termed a 'hair colorant' which covers all types of colouring products (temporary, semi- or demi-permanent and permanent). The products will always carry warning labels and use instructions. Users are advised to carry out an allergy alert test before applying the product in full. It is important to always follow the manufacturers' instructions.

Are hair dyes and colorants safe?

Hair colorants are one of the most thoroughly studied consumer products on the market and their safety is supported by a wealth of scientific research. As with any other cosmetic product, European cosmetic safety laws require that they must not cause harm to human health. Before any product reaches the shelf it must have undergone a rigorous safety assessment by a professionally qualified safety assessor before placing a cosmetic product on the market. The assessment takes into account the finished product, all of the ingredients (irrespective of their source), how and where the product is to be used, how often and by whom. The assessment will also guide the manufacturer in providing clear warnings and instructions - which often go further than is required by law.

There are sometimes rumours that hair colorants cause cancer. Is this true?

The chemistry of how hair dyes work is well known and their safety is supported by a wealth of scientific research.

Scientific bodies regularly review scientific studies on hair colorants and no link has been found between the use of hair colorants and any type of cancer.

In 2008 the International Agency for Research on Cancer (IARC) reviewed hair dye use. It concluded that there is inadequate evidence for a link between personal hair use and cancer. This reflects its major review in 1993 which looked at 70 published reports on hair colorants.

83 additional studies were performed between 1993 and 2003 and were reviewed by the Johns Hopkins University School of Public Health in the US. This substantial review also concluded that there was no proven relationship between hair colorants and cancer.

In a 2020 study, US researchers investigated whether regular hair colouring increases the risk of cancer. A research team collected data from more than 117,000 women over a period of 36 years. It is the largest study ever carried out on the subject. The study again confirms that there is no relationship between personal regular use of permanent hair colours and an increased risk of developing cancer.1

I have heard the European Commission recently banned some hair dyes because they cause cancer. Is this true?

No. The European Commission, in partnership with the European cosmetics industry, is in the process of a comprehensive regulatory review of hair dyes. This has included the banning of several hair dyes as one part of this review. However, it must be stressed that the hair dyes have been banned not because of any particular risk, but because the cosmetics industry has declared no interest for their further use in hair colorants.

Is there a cancer risk for hairdressers or consumers?

No. There is no scientific evidence for a causal link between hair colouring and cancer. Hair colorants for hairdressers and consumers are safe and have been extensively assessed for safety.

Can I colour my hair whilst I'm pregnant or breastfeeding?

Colouring your hair when you are breastfeeding or pregnant is perfectly safe. As always, it is really important to make sure you follow the product instructions and carry out the allergy alert test as directed 48 hours before colouring your hair. However, some women can be extremely concerned about colouring their hair at this time and for them it is better to avoid the source of anxiety and not have their hair coloured - even though there are no safety concerns from the colouring itself.


1Zhang et al (2020) Personal use of permanent hair dyes and cancer risk and mortality in US women: prospective cohort study. BMJ 2020; 370.

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