Is Methenamine safe during pregnancy?
A preservative that slowly releases small amounts of formaldehyde. Usually fine in rinse-off products; a common allergen.
What the sources say
Methenamine is a formaldehyde-releasing preservative; release rises with heat, time and water content. Formaldehyde is a known human carcinogen and allergen (NIEHS), and MotherToBaby notes studies of workers around formaldehyde suggested a higher chance of miscarriage, though cosmetic preservative levels are far lower. No pregnancy studies of preservative-level use exist. Limit: prefer rinse-off products or releaser-free leave-ons when easy; never heat-activated formaldehyde hair treatments.
Also listed as
hexamethylenetetramine, hexamine, urotropin
Sources
- NIH PubMed (peer-reviewed study): Investigation on formaldehyde release from preservatives in cosmetics (Int J Cosmet Sci, 2015)
- MotherToBaby: Hair Treatments
- NIH NIEHS: Cosmetics and Your Health: NIEHS Research Findings (fact sheet, Jan 2024)
Last reviewed . This is general information, not medical advice. Ask your doctor or midwife about your own situation.