Sodium Hydroxymethylglycinate

Sodium hydroxymethylglycinate is a preservative (formaldehyde-releasing) typically used at low concentrations (~0.1–0.5%), but it has documented potential to cause irritant reactions and, more importantly, allergic contact dermatitis in sensitized individuals. In eczema-prone and barrier-compromised skin, formaldehyde releasers are a higher-risk category due to delayed sensitization and cumulative exposure from multiple products. Given its preservative role and clinically recognized sensitization potential even at typical use levels, it warrants a notable irritancy score with careful use and patch testing in sensitive populations. Safety Notes: Sodium hydroxymethylglycinate is used in consumer cosmetics primarily as a formaldehyde-releasing preservative, with real-world leave-on products (lotions, creams, serums) often formulated around ~0.1–0.3% and some rinse-off cleansers at similar or slightly higher levels depending on preservative system load. The lowest observed commercial uses are around 0.05% when paired with additional preservatives/chelators and low microbial risk formats, while the highest consumer-available uses approach ~0.5% in higher-challenge systems seeking broad-spectrum preservation. In the EU it is regulated with a maximum of 0.5% (as sodium hydroxymethylglycinate), which effectively caps the top end seen in mainstream OTC products.