Should expectant mothers use hair dye?

Jina Kum
10 July 2015

Above: Image ©

Dyeing your hair is a great way to change your look. About 45% of women and 6% of men in United States and Canada have dyed their hair, just like millions of other people around the world. However, a common concern is whether it is safe to use hair dye during pregnancy, especially whether it can harm the fetus.

The health of the fetus is of special concern because the placenta is a permeable membrane that can transfer nutrients and chemicals from a mother’s blood to her unborn child. In particular, the fetus is very susceptible to carcinogens as its immune system is not fully developed.

Did you know? Pregnancy may cause an expectant mother’s hair to react differently to hair dyes.Although a variety of different studies have found an association between hair dye use and health problems in pregnant women and their children, no causal relationship between the two has been established.

In the case of one couple who experienced long-term exposure to hair dye, their infant children were found to have chromosomal mutations. Chromosomes are an organism’s genetic blueprint, so any mutations can negatively affect the growth of an embryo. And although the parents themselves had normal chromosomes, they did experience other symptoms, including weakened immune systems, dizziness, and headaches. While the health effects of the chromosomal mutations experienced by the children are unclear, other studies have suggested that the risk of germ-cell tumours is increased in children of mothers exposed to hair dye during pregnancy and breastfeeding.

Furthermore, different chemicals found in hair dye may be harmful to pregnant women. For example, para-phenylenediamine (a benzene ring with two NH2 groups attached) and has been associated with severe facial swelling, skin inflammation, and dermatitis in pregnant women. This chemical has also been found to increase the incidence of mammary gland (breast tissue) tumours in female rats, as well as induce tumours in other organs in male rats, including kidney and liver tumours.

Did you know? Health Canada requires that hair dyes containing para-phenylenediamine be labelled with a warning about potential allergic reactions.Research has shown that N-nitroso compounds (molecules that contain carbon, nitrogen, and oxygen atoms) also have carcinogenic (cancer-causing) characteristics. After many studies showed how these compounds can initiate tumour formation in mice, a group of California researchers investigated whether there was a link between N-nitroso compounds in hair-colouring products and childhood brain tumours. Although the results of the study provided “no consistent evidence of an association between risk for CBT and use of hair dyes during pregnancy”, an elevated risk brain tumours was observed in some children whose mothers used hair dye immediately before pregnancy. However, the researchers were not able to determine if this was due to hair dye or other factors.

Yet another study has associated the use of hair dye during the first and second trimesters of pregnancy with a twofold increase in the risk of neuroblastoma, the most common type of solid tumour in children. Incidence of neuroblastoma peaks in infancy, and its causes have not been identified.

When interpreting the results of these different studies, it is important to distinguish between causation and association. On the one hand, several research studies have found a relationship between the use of hair dyes by pregnant women and health problems in fetuses, children, and adults. On the other hand, they have been unable to demonstrate that using hair dye during pregnancy actually causes the health problems that have been observed. Getting clearer answers to questions about the risks associated with using hair dye during pregnancy will therefore probably require large-scale longitudinal studies that follow the health of a large group of people over a long period of time.

Learn more!

Safety of Cosmetic Ingredients (2015)
Health Canada

Hair Treatment During Pregnancy (2014)
American Pregnancy Association

Hair Dyes (2014)
American Cancer Society

Websites with general information on the safety of hair dyes and other cosmetics.

Chemistry colour conundrum: Choosing a hair dye (2015)
Catherine Chan, CurioCity by Let’s Talk Science

Are hair dyes safe (2014)
Catherine Chan, CurioCity by Let’s Talk Science

What’s your shade (2011)
Laura Jamieson, CurioCity by Let’s Talk Science

Hair to DYE for… (2006)
CurioCity by Let’s Talk Science

Other CurioCity articles discussing hair dyes.

Risk of neuroblastoma, maternal characteristics and perinatal exposures: the SETIL study (2014)
S. Parodi et al., Cancer Epidemiology 38

Severe facial swelling in a pregnant woman after using hair dye (2014)
M. E. van Genderen, G. Carels, E. R Lonnee & A. Dees, BMJ Case Reports

Is there a true concern regarding the use of hair dye and malignancy development? (2013)
P. Saitta et al., Journal of Clinical and Aesthetic Dermatology 6

Hair Dye Use and Risk of Adult Acute Leukemia (2004)
G. H. Rauscher, D. Shore & D. P. Sandler, American Journal of Epidemiology 160

West Coast study of childhood brain tumours and maternal use of hair-colouring products (2002)

E. A. Holly, P. M. Bracci, M. Hong, B. A Mueller & S. Preston-Martin, Paediatric and Perinatal Epidemiology 16
Link to abstract. Registration or subscription required to view full text.

Carcinogenicity of an oxidation product of p-phenylenediamine (1986)
W. Rojanapo, P. Kupradinun, A. Tepsuwan, S. Chutimataewin & M. Tanyakaset, Carcinogenesis 7
Link to abstract. Registration or subscription required to view full text.

Scientific articles on health risks associated with hair dye.

Trends in use of hair dye: a cross-sectional study (2013)
D. Patel, S. Narayana & B. Krishnaswamy, International Journal of Trichology 5

Scientific article on a study of hair dye use in India.

Jina Kum

I am a graduate student at Western University. Born in South Korean, I moved to Toronto at the age of 6 and have lived in Canada since then. I enjoy camping - especially the campfire and the stars! I love science because it helps to explain the natural world, from why sky is blue to how we can generate new treatments to fight diseases. 

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