There are three types of hair dyes in use:
- Temporary dyes that wash out after one shampoo
- Semipermanent dyes that wash out after several washes
- Permanent/oxidation dyes that last until the hair grows out
Each preparation contains numerous ingredients that have varied over the years. For example hair dyes containing lead, used to color the
hair black, are no longer in common usage except for lead acetate dyes used in Grecian Formula.
In addition many formulations were changed in the late 1970s when manufacturers
removed ingredients linked to the development of cancer in animals .
While studies on the use of hair dyes in human pregnancy are scarce several
animal studies are reassuring. One study of 12 hair dye
formulations (three semipermanent and nine oxidations dyes mixed 1:1 with 6%
hydrogen peroxide) found no evidence of impaired fertility or harm to the
fetus after topical application in pregnant rats  . Another study found no
developmental defects in the offspring of pregnant rats fed five oxidative
dyes at doses
greater than 100 times the usual human
exposure . Some preparations have been associated with birth defects in mice at doses
that were usually toxic to the mother [4,5].
The quantity of dye used in these animal experiments
far exceeds the amount a woman would receive from routinely coloring her hair. In
addition hair colorants would not be expected to be harmful with occasional use
because the amount of hair dye absorbed through the skin is so small [2, 6-8].
Many human studies have asked women to look backward in their medical
histories to look for an exposure that might be related to
either some birth defect or other outcome (retrospective studies). It is important to remember that the
results of such retrospective studies may sometimes be influenced by the accuracy or
completeness of events recalled to memory.
One retrospective study from Sweden sent questionnaires to 3706 hairdressers and
3462 women who acted as controls. The response rate was 65%.
Compared with the controls, the hairdressers more often gave birth to infants
that were small for gestational age (SGA), and were more likely to have an
infant with a major malformation (2.8% v 2.1%). Frequent permanent waving and
spraying tended to be associated with increased risk of having an SGA infant,
whereas no clear association could be seen between the individual exposure
assessments and malformation risk .
In contrast information collected prospectively from the Swedish Medical Birth
Register on 12 ,046 infants born to female hairdressers failed to find an
increased risk for malformations in the infants of hairdressers compared to non
hairdressers. However, this prospective study did confirm that full-time hairdressers more often had intrauterine
growth-restricted infants (ie, small for gestational age) as compared with
nonhairdressers with a corresponding worktime .
The potential for the development of cancer in the offspring of women exposed to hair dyes while pregnant has also been of concern.
To date studies have found no consistent
evidence of an association between the risk for childhood brain tumors (CBT) and
of hair dyes during pregnancy [11,12].
One case-control study found that the use of any hair dye in the month before
and/or during pregnancy was associated with a moderately increased risk of neuroblastoma
in the offspring of exposed women. Temporary hair dye use was more strongly
associated with neuroblastoma than use of permanent hair dye . Then again,
the development of neuroblastoma has been associated with several prenatal
exposures as well as folic acid deficiency [14-16].
Overall there is no definite evidence that the use of hair colorants during pregnancy is
harmful. In addition hair colorants would not be expected to be harmful with occasional use because the amount of hair dye absorbed through the skin is
so small. Highlighting which doesn't touch the scalp probably poses no
Nonetheless, the scientific evidence is too limited to give
to draw firm conclusions for or against the use of hair colorants during
pregnancy. There are no studies to suggest that “natural” products are safer than man-made ones.
Any potential for harm may be reduced by taking the following precautions:
- Avoid the use of hair dyes during the first trimester.
- Use protective gloves.
- Work in a well ventilated area.
- Do not leave the dye on the hair any longer than necessary.
- Rinse the scalp thoroughly after the use of hair dye.
- Reduce the frequency of hair dying.
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Hazards: A Guide for Clinicians Baltimore: Williams and Wilkins 366-367.
2. Burnett C, et al. Teratology and percutaneous toxicity studies on hair dyes.J Toxicol Environ
3. DiNardo JC, et al. Teratological assessment of five oxidative hair dyes in the rat.Toxicol
Appl Pharmacol. 1985 Mar 30;78(1):163-6.
4. Inouye M and Murakami U.Teratogenicity of 2,5-diaminotoluene, a hair-dye constituent, in
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5. Marks ta, et al. Teratogenic evaluation of 2-nitro-p-phenylenediamine,
4-nitro-o-phenylenediamine, and 2,5-toluenediamine sulfate in the mouse.Teratology. 1981;24(3):253-65.
6.Wolfram LJ et al, Percutaneous penetration of hair dyes.Arch Dermatol Res. 1985;277:235-41.
7.Maibach HI, et al. Percutaneous penetration following use of hair dyes.Arch Dermatol. 1975;111(11):1444-5.
8. Bronaugh RL and Congdon ER.Percutaneous absorption of hair dyes: correlation with partition coefficients.
J Invest Dermatol. 1984 ;83(2):124-7.
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10.Rylander L and Källén B.Reproductive outcomes among hairdressers.Scand J Work Environ Health. 2005;31(3):212-7.
11.Holly EA et al. West Coast study of childhood brain tumours and maternal use
of hair-colouring products.Paediatr Perinat Epidemiol. 2002;16(3):226-35.
12. Efird JT, et al, Beauty product-related exposures and childhood brain tumors in seven countries: results from the SEARCH International Brain Tumor Study.J Neurooncol. 2005;72(2):133-47.
13. McCall EE, et al. Maternal hair dye use and risk of neuroblastoma in offspring. Cancer Causes Control. 2005 Aug;16(6):743-8.
14.Cook MN, et al. Maternal medication use and neuroblastoma in offspring.Am J Epidemiol. 2004 Apr 15;159(8):721-31.
15. Bkuhm EC et al., Maternal use of recreational drugs and neuroblastoma in
offspring: a report from the Children's Oncology Group (United States).Cancer Causes
16. French AE ,et al., Folic acid food fortification is associated with a decline
in neuroblastoma.Clin Pharmacol Ther.2003;74(3):288-94.
Reviewed: Mark A. Curran, M.D.