“Can I get a keratin treatment or hair straightening while I'm pregnant?”

The clinical answer isn't a simple “yes” or “no”. In Brazil, “progressiva” is a broad trade name for techniques that smooth the hair fiber and reduce volume. The chemical formulas involved vary dramatically from one manufacturer to another.

The most prudent obstetric recommendation is to avoid any chemical straightening procedure during pregnancy, especially formulas containing formaldehyde, glutaraldehyde or acidic substances that release toxic fumes when heated. It is not enough for the salon to label the procedure “organic” or “formaldehyde-free”; you must check the product's technical composition and its health registration.

1. The Health Alert: Why Is Formaldehyde Banned? In Brazil, the National Health Surveillance Agency (Anvisa) expressly prohibits the use of formaldehyde (formol) as a hair-straightening agent for anyone, pregnant or not. Legislation and Health Crime: Formaldehyde is authorized only as a preservative at a maximum residual concentration of 0.2%. Adding pure formaldehyde to hair creams is a serious health violation and a heinous crime against public health (Article 273 of the Brazilian Penal Code).

Toxic and Carcinogenic Potential: Formaldehyde is classified by the World Health Organization (WHO) as a substance known to cause cancer in humans. Pregnancy Risks: Chronic or high-concentration inhalation of formaldehyde fumes has been associated in occupational studies with a higher risk of miscarriage, fetal growth restriction and respiratory toxicity in the mother.

2. The Illusion of "Organic Treatments": Glyoxylic Acid The phrase “formaldehyde-free” does not mean biological safety during pregnancy. Many products sold as "acid straightening", "organic blowout", "thermal sealing" or "hair botox" use glyoxylic acid. Anvisa Alert: Anvisa warns that glyoxylic acid, when exposed to high temperatures from a hair dryer or flat iron, can undergo thermal decomposition and release formaldehyde fumes into the air. In addition, toxicology literature and pharmacovigilance reports link the absorption of derived compounds through the skin to serious episodes of kidney disease and acute kidney injury.

3. The Organogenesis Window: The first trimester of pregnancy (from conception to 13 weeks and 6 days) covers organogenesis, the phase when the embryo's organs are formed and the neural tube closes. In this phase, the fetus is extremely susceptible to environmental teratogens and endocrine disruptors. Even for hair procedures with low skin absorption on an intact scalp (such as certain ammonia-free toners), the Brazilian Society of Dermatology (SBD) and FEBRASGO recommend stopping all chemical hair treatments completely in the first trimester.

Reaching 12 weeks does not automatically make chemical straightening treatments okay. Inhaling volatile fumes remains a route of exposure throughout pregnancy.

4. What If You Straightened Your Hair Before Finding Out You Were Pregnant?

If you had a straightening treatment and found out you were pregnant days or weeks later: don't panic. A one-time exposure rarely reaches systemic teratogenic doses capable of causing isolated birth defects. Acute maternal stress is more harmful than what has already happened. Look into the product: if possible, ask the salon for the manufacturer's name, the batch and the label of the cosmetic used. Mention it at your prenatal care visit. Tell your health team (family doctor or obstetrician).

Routine anatomy scans will carefully assess the baby's anatomy. Acute respiratory symptoms: If you had severe shortness of breath, coughing fits or chemical burns on your scalp after the procedure, seek medical care.

5. The Difference Between Hair Dye, Highlights and Straightening Not every hair procedure carries the same risks:

Chemical straightening: Involves heat, breaking the disulfide bonds of keratin and releasing volatile fumes that can be inhaled and absorbed through the skin. It carries the highest toxicological risk.

Permanent hair dyes: Have low absorption through the skin when applied to an intact scalp. Many obstetric teams allow ammonia-free colors from the second trimester.

Highlights and streaks with a cap or foil: Since the bleaching product does not touch the skin of the scalp, systemic absorption is minimal, making this a more accepted alternative in the second and third trimesters.

6. Occupational Risks: Hairdressers and Beauty Professionals For pregnant women who work as hairdressers or salon assistants, exposure is no longer occasional but daily and prolonged. Workstations need to be adapted: requiring Personal Protective Equipment (masks with organic vapor filters, nitrile gloves), keeping mechanical ventilation with exhaust fans and, ideally, being moved away from handling volatile products during pregnancy.

7. Safety Criteria and Risk-Free Self-Care Self-care and the pregnant woman's well-being are fundamental. Keeping up your self-esteem is part of mental health during pregnancy, but without exposing the fetus to unnecessary substances. Choose temporary physical and heat-based methods: Traditional blowout and styling with a hair dryer (using only heat protectants and simple moisturizing leave-ins, with no added acids or formaldehyde); Hair Care Schedule and Oil Treatments: nourishing formulas based on 100% pure plant oils (such as coconut oil, avocado oil or shea butter) help seal the cuticles and control volume without chemical modification; Always Check the Label.

Legal straightening cosmetics must carry the mandatory warning required by Anvisa: "For use by pregnant and breastfeeding women, consult a doctor". If the product does not have this information or has been repackaged into generic containers, throw it away.

References

National Health Surveillance Agency (Anvisa). Formaldehyde cannot be used in hair straighteners. Brasília: Anvisa.

National Health Surveillance Agency (Anvisa). Alert on the use of glyoxylic acid and toxicological risks in hair cosmetics. General Management of Cosmetics (GGCOS). Brasília: Anvisa. Brazil. Ministry of Health. Low-risk prenatal care ("Atenção ao pré-natal de baixo risco", Primary Care Notebooks, No. 32). Brasília: Ministry of Health.

Brazilian Federation of Gynecology and Obstetrics Associations (FEBRASGO). Environmental and occupational exposures in pregnancy. Prenatal Care Guidance Manual. São Paulo: FEBRASGO.

Organization of Teratology Information Specialists (OTIS) / MotherToBaby. Hair Treatments and Pregnancy. Fact Sheet. United States.