Formaldehyde and Formaldehyde-Releasing Preservatives in Pregnancy
Formaldehyde is a known irritant and carcinogen, and it appears directly or indirectly in some beauty products. The MamaSkin ingredient dataset separates higher-risk formaldehyde sources from lower-risk releasers.
Why this category matters in pregnancy
Formaldehyde-related ingredients are used in some salon treatments and preservatives, which can lead to higher-than-expected exposure through both skin contact and inhalation. Pregnancy skin is often more reactive, and barrier changes can make common sensitizers feel harsher. Frequent treatments or large-area application can increase contact, so exposure depends heavily on how and where products are used. Guidance is conservative for formaldehyde itself, while some releasers are treated as lower risk but still noted for sensitization, and many people choose extra caution early in pregnancy before reassessing with a clinician.
How these ingredients work and why they are popular
Formaldehyde and formaldehyde-releasing preservatives prevent microbial growth, and releasers emit small amounts of formaldehyde over time to keep formulas stable. They are used because they are effective at low levels and can improve durability or wear time in certain treatments.
Where they appear and common misconceptions
These ingredients can appear in hair smoothing or straightening treatments, nail hardeners, shampoos, cleansers, and some leave-on cosmetics, so exposure is not limited to one product type. Common misconceptions include assuming a product marketed as gentle cannot contain formaldehyde releasers, that low percentages guarantee no sensitization, and that wash-off use removes inhalation concerns in salon settings.
Ingredient snapshot
- Formaldehyde (high risk): IARC group 1 carcinogen; limited pregnancy data but irritant concerns warrant avoidance.
- Formalin (high risk): Aqueous formaldehyde solution; same risk band.
- Methanediol (high risk): Formaldehyde-releasing agent used in some hair straighteners.
- DMDM hydantoin (low risk): Formaldehyde-releasing preservative; sensitiser with no teratogenic signal.
- Imidazolidinyl urea (low risk): Weak sensitiser; no reproductive toxicity signal.
- Diazolidinyl urea (low risk): Sensitisation risk noted; no reproductive toxicity signal.
Where they appear
- Hair smoothing or straightening treatments.
- Certain nail treatments or hardeners.
- Preservatives in liquid cosmetics and cleansers.
How to reduce exposure
- Avoid formaldehyde and formalin whenever possible, especially in salon treatments.
- If you are sensitive, choose fragrance-free and formaldehyde-free formulas.
- Scan every product label to spot releasers that are not obvious.
Read next
- Ingredients to Avoid in Pregnancy (Quick List)
- Pregnancy-Safe Deodorants 2025
- Pregnancy-Safe Skincare Picks 2025
Check products with MamaSkin
- Scan labels to see if formaldehyde releasers are present.
- Compare alternatives by risk band.
- Save safer picks before you shop.
Download MamaSkin (iOS & Android): App Store | Google Play
FAQs
Is formaldehyde safe during pregnancy?
Formaldehyde and formalin are high risk in our dataset due to carcinogen and irritant concerns.
Are formaldehyde releasers all high risk?
No. Several releasers are low risk in our dataset but still carry sensitisation concerns.
Where do these ingredients show up?
They appear in some hair treatments, nail products, and preservatives in skincare.