Hair Dye & Hair Treatments
Everyday exposureBeauty & personal careAlso called · 15 names▾▴
hair dye, hair color, hair coloring, highlights, perm, permanent wave, hair bleach, relaxer, hair straightening, hair colouring, bleach during pregnancy, hair highlights, semi permanent dye, permanent hair color, hair dye pregnant
Hair
General information · effects depend on amount, timing, and how it is used. About these sources
- Topical
Research strength: 3 / 5
MotherToBaby and ACOG report that little dye is absorbed through healthy scalp skin when products are used as directed. The NHS says someone might choose to wait until after 12 weeks, while ACOG describes low absorption. Uccella et al. found low or very low certainty observational evidence, and its stillbirth signal involved repeated occupational use rather than personal use. The FDA says some heated smoothing products release formaldehyde gas, which is a separate product and inhalation concern. Ask your provider about your situation.
Last reviewed: 2026-10-14
Sources
- MotherToBaby: Hair TreatmentsTeratology service
- ACOG: Hair dye during pregnancyProfessional society
- NHS: Using hair dye in pregnancyUK government
- Uccella et al. 2026: Hair Dyes in PregnancyUS government
- Ooka et al. 2021: Japan Environment and Children’s StudyUS government
- FDA: Hair Smoothing Products and FormaldehydeUS government
Research strength: 3 / 5
MotherToBaby and ACOG report low absorption of hair dye through healthy scalp skin when products are used as directed. Uccella et al. found that many studies did not identify the dye type or exposure timing, so the review does not give a clear second trimester estimate. Ooka et al. reported a stillbirth association with repeated occupational dye use across the first and later trimesters, while personal use was not significantly associated. The FDA says some heated smoothing products release formaldehyde into the air, especially where ventilation is poor. Ask your provider about your situation.
Last reviewed: 2026-10-14
Research strength: 3 / 5
MotherToBaby and ACOG report low absorption of hair dye through healthy scalp skin when products are used as directed. The reviewed studies do not establish a third trimester effect from a personal hair treatment. Uccella et al. describe low or very low certainty observational findings, and Ooka et al.'s stillbirth signal involved repeated occupational exposure across pregnancy. The FDA separately warns that some heated smoothing products release formaldehyde gas, with inhalation concerns in poorly ventilated salons. Ask your provider about your situation.
Last reviewed: 2026-10-14
Hair Dye & Hair Treatments — Breastfeeding
Research strength: 2 / 5
MotherToBaby estimates that large amounts of hair-care chemicals are unlikely to enter milk when products are used as directed on healthy, unbroken skin, based on low expected absorption into the blood. Its fact sheet does not report direct milk measurements or infant outcome studies. Two case-control studies reported associations between maternal hair-product use during breastfeeding and childhood cancer outcomes, but neither measured chemicals in milk or established cause. The evidence is too limited to judge infant exposure for specific treatments. Ask your provider about your situation.
Last reviewed: 2026-10-14
Pregnancy
Uccella et al. (2026) reviewed 20 observational studies and rated the certainty of evidence low or very low. In the Japan Environment and Children’s Study, Ooka et al. (2021) analyzed 104,065 fetuses. First trimester occupational hair dye exposure was not significantly associated with spontaneous abortion. Repeated occupational use from the first through second or third trimester was associated with stillbirth: adjusted OR 4.92 (95% CI 1.53 to 15.78) for 1 to 6 times a week and 7.59 (95% CI 2.32 to 24.85) for daily use. Frequent personal use at home or a salon was not statistically significant in that study. Siegel et al. (2022) analyzed National Birth Defects Prevention Study data and found an association between hairdressing work and cleft lip with cleft palate (OR 2.0, 95% CI 1.1 to 3.7), but only 196 hairdresser mothers were included and the authors noted wide confidence intervals. These occupational findings do not establish an effect from a personal appointment. Axmon et al. (2006) found no overall cohort difference in miscarriage risk among hairdressers, and hair-treatment estimates were not statistically significant. The MotherToBaby statement about miscarriage among formaldehyde-exposed workers was not verified against a formaldehyde-specific primary study and is not carried forward. Recent evidence includes Tsui et al. (2026), a feasibility intervention with 46 participants that studied product-use behavior and urine phthalate metabolites, not pregnancy or infant clinical outcomes. Greene et al. (2025) reviewed 96 cancer articles, including five on maternal exposure and pediatric cancer; it does not add direct milk-transfer evidence.
Breastfeeding
Two case-control studies reported childhood cancer associations based on maternal reports of hair-product exposure during breastfeeding. Couto et al. (2013) reported an adjusted OR of 2.43 (95% CI 1.13 to 5.22) for acute myeloid leukemia among children under age two. Chen et al. (2006) reported a germ cell tumor OR of 1.5 (95% CI 1.0 to 2.2) for boys and girls together and 1.7 (95% CI 1.1 to 2.6) for girls. Neither study measured hair-product chemicals in breast milk or established that exposure caused the outcomes. Chen et al. concluded that the study produced no strong evidence overall and that the significant findings needed confirmation. MotherToBaby's transfer estimate is based on small expected maternal blood absorption, not measured milk concentrations. No LactMed monograph for hair treatments was found in the reviewed source set.
Hair treatments include temporary, semi-permanent, and permanent dyes, bleach, perms, and relaxers. MotherToBaby lists hydrogen peroxide and ammonia among common hair dye chemicals, hydrogen peroxide in bleach, and several chemicals used in perms and relaxers. Formulas vary by product. The FDA says some heated smoothing products contain formaldehyde, formalin, or methylene glycol and can release formaldehyde gas when heated. Findings about dye use should not be treated as product-specific evidence for bleach, perms, or smoothing treatments.
What was tested
Ooka et al. used participant questionnaires about occupational chemical use in the first and second or third trimesters and daily hair dye use at home or in salons; the study did not use biomonitoring. The primary outcome analyses were based on pregnancy records and physician-confirmed fetal outcomes. Siegel et al. classified self-reported maternal occupations during early pregnancy and compared hairdressers with non-cosmetology workers. Couto et al. and Chen et al. used parent-reported exposure histories and case-control designs for childhood cancer outcomes. None of these studies measured hair-treatment chemicals in breast milk or estimated infant dose through milk.
Whether to delay a personal hair dye appointment until after 12 weeks
- Source A says
- The NHS says someone might choose to wait until after the first 12 weeks, when it describes the chance of chemical harm as lower. (NHS: Using hair dye in pregnancy)
- Source B says
- ACOG reports that only a small amount of hair dye chemicals is absorbed through the scalp. Uccella et al. found low or very low certainty observational evidence and noted that few studies distinguished dye type or exposure timing. (ACOG: Hair dye during pregnancy, Uccella et al. 2026: Hair Dyes in Pregnancy)
- Why they differ
- The NHS presents an optional timing precaution, while ACOG emphasizes low absorption and the review describes uncertain observational evidence. The reviewed studies do not compare waiting until 12 weeks with having a personal appointment earlier.
- What the evidence shows overall
- This is a difference in caution, not evidence that an early personal appointment causes harm or that delaying changes an outcome. Keep the pregnancy rating at guidance and retain 3 research stars, while attributing the optional timing statement.
- MotherToBaby describes highlights and similar methods that apply color to the hair shaft without touching the skin. (MotherToBaby: Hair Treatments)
- The NHS describes wearing gloves, using a well-ventilated room, limiting application time, and rinsing the scalp thoroughly as ways to reduce contact during hair coloring. (NHS: Using hair dye in pregnancy)
- The FDA describes following package directions, patch testing, wearing gloves, and rinsing the scalp after dye use. (FDA: Hair Dye and Hair Relaxers)
General research, not specific to pregnancy.
The FDA describes a separate inhalation and contact concern for some heated hair-smoothing products. This is not evidence that routine hair dye use causes pregnancy outcomes.
- The FDA says some heated smoothing products release formaldehyde gas, which salon workers and clients may inhale when ventilation is poor. (FDA: Hair Smoothing Products That Release Formaldehyde When Heated)
- The FDA describes irritation to the eyes, nose, lungs, and skin, and notes that high or prolonged formaldehyde exposure has been linked to certain cancers. (FDA: Hair Smoothing Products That Release Formaldehyde When Heated)
- The 2026 Unified Agenda lists the formaldehyde action for heated hair-smoothing products at the proposed-rule stage, not as a finalized restriction. (FDA: Formaldehyde in Hair Smoothing Products, Unified Agenda)
- MotherToBaby: Hair TreatmentsTeratology serviceSecondaryPage dated 2026-06-01
- ACOG: Hair dye during pregnancyProfessional societySecondaryIndependent check
- NHS: Using hair dye in pregnancyUK governmentSecondaryPage dated 2023-09-27Independent check
- FDA: Hair Dye and Hair RelaxersUS governmentSecondaryPage dated 2022-06-27
- FDA: Hair Smoothing Products That Release Formaldehyde When HeatedUS governmentSecondaryPage dated 2024-10-15Independent check
- FDA: Formaldehyde in Hair Smoothing Products, Unified AgendaSecondary
- Uccella et al. 2026: Hair Dyes in PregnancyUS governmentPrimaryPage dated 2026-05-21Independent check
- Ooka et al. 2021: Japan Environment and Children’s StudyUS governmentPrimaryIndependent check
- Siegel et al. 2022: Hairdresser occupation and birth defectsUS governmentPrimaryIndependent check
- Axmon et al. 2006: Hairdresser work and miscarriageUS governmentPrimaryIndependent check
- Couto et al. 2013: Hair products and early age leukemiaUS governmentPrimaryIndependent check
- Chen et al. 2006: Maternal exposures and childhood germ cell tumorsUS governmentPrimaryIndependent check
- Tsui et al. 2026: Hair care product use among pregnant women of colorUS governmentPrimary
- Greene et al. 2025: Hair dye use and human cancersUS governmentPrimary
Last reviewed 2026-10-14
Independent check 2026-10-14
Not yet clinician-reviewed
Ask your provider about your situation.