What Is It?

Methenamine, also called Hexamethylenetetramine, occurs as crystals, granules, or powder. In cosmetics and personal care products, Methenamine is used in the formulation of eye makeup, as well as shampoo and hair conditioners.

Why Is It Used?

Methenamine functions as a cosmetic biocide and a preservative.

Follow this link for more information about how preservatives protect cosmetics and personal care products.

Scientific Facts

A related compound, methenamine hippurate, is used for the treatment of urinary tract infections.

Safety Information

The Food and Drug Administration (FDA) includes Methenamine on its list of indirect food additives. It is permitted for use as a component of adhesives, polymers, and paper and paperboard having incidental contact with food. The safety of Methenamine has been assessed by the Cosmetic Ingredient Review (CIR) Expert Panel. The CIR Expert Panel evaluated the scientific data and concluded that Methenamine was safe for cosmetic use at concentrations not to exceed 0.16%. The CIR Expert Panel did not conclude that Methenamine was safe for use in cosmetics and personal care products intended to be aerosolized.

CIR Safety Review: Methenamine, following oral administration, was hydrolyzed and formaldehyde was generated. Methenamine was rapidly absorbed from the intestinal tract and excreted mostly unchanged in the urine. No adverse signs of toxicity were observed in either subchronic or chronic studies. Methenamine was slightly irritating to the skin. In ocular studies it was mildly irritating.

Methenamine was a sensitizer when tested at a concentration of 25%, but not at 0.2%. It was neither an irritant nor a sensitizer to humans at 0.1%. In a number of reproductive and developmental toxicity studies, no developmental effects attributable to Methenamine were observed. Methenamine was a mutagen in fruit flies but not in other in vitro mutagenicity assays. Methenamine did not show any carcinogenic activity, either alone or when nitrite was included in the drinking water. Methenamine was judged to be safe for non-aerosolized cosmetics and personal care products at a concentration not to exceed 0.16%. At this concentration, the released formaldehyde concentration does not exceed 0.2%.

More information about formaldehyde.

Link to FDA Code of Federal Regulations for Hexmethylenetetramine (Methenamine)

The Joint FAO/WHO Expert Committee on Food Additives has established an Acceptable Daily Intake of 0-0.15 mg/kg body weight for Methenamine.

Methenamine is listed as Hexamethylenetetramine in the Cosmetics Directive of the European Union (see Annex VI) and may be used as a preservative at a maximum concentration of 0.15%. All finished products containing formaldehyde must be labelled with the warning “contains formaldehyde” where the concentration of formaldehyde in the finished product exceeds 0.05%.

Link to the EU Cosmetic Regulation:…

More Scientific Information

Methenamine is an organic amine. At low pH, Methenamine undergoes hydrolysis and liberates formaldehyde. In cosmetics and personal care products, Methenamine functions as a cosmetic biocide and a preservative.


Find out more about the regulation of Food Additives by the Food and Drug Administration

Food Ingredients and Packaging:

Food Contact Substances:…

Substances Generally Recognized As Safe (GRAS):

Search the Code of Federal Regulations

EU Cosmetics Inventory