Sodium Hydroxymethylglycinate
A formaldehyde-releasing preservative dressed up as "natural" — derived from an amino acid, but it still releases formaldehyde
INCISodium Hydroxymethylglycinate
- Category
- Preservative
- Risk level
- medium
- What it is
- A glycine-derived, formaldehyde-releasing preservative (trade name Suttocide A)
- The "natural" trap
- Amino-acid origin gets it marketed as gentle/natural — but it releases formaldehyde like any other releaser
- Cross-reaction
- A reaction predicts sensitivity to DMDM hydantoin, quaternium-15, imidazolidinyl/diazolidinyl urea, bronopol, and free formaldehyde
- Where it hides
- Disproportionately in "clean"/natural products and leave-on lotions
Look for these names on ingredient lists
This ingredient may appear under any of these names:
Commonly found in
Possible reactions
- Allergic contact dermatitis in formaldehyde-sensitive people
- Redness and itching at the application site
- Eczema flare with continued use
- Often unexpected, since it hides in "natural" products
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What is sodium hydroxymethylglycinate?
Sodium hydroxymethylglycinate (trade name Suttocide A, sometimes abbreviated SHG) is a preservative made by hydroxymethylating glycine, the simplest amino acid. That amino-acid origin is the key to its reputation — and its trap. Chemically it belongs to the formaldehyde-releasing preservative family: it contains no free formaldehyde but slowly releases it under the pH and temperature of skincare formulas, and that released formaldehyde is what does the preserving.
It's used at 0.1–0.5% in water-based products — and, tellingly, often in "natural" or "clean" formulations marketed as free from harsh chemicals.
Why it causes reactions (and why it surprises people)
Like all formaldehyde releasers, SHG causes contact allergy through the formaldehyde it generates, which binds skin proteins and triggers a delayed (Type IV) reaction in sensitised people. The honest point: the "natural" amino-acid framing is irrelevant to allergy — your skin reacts to the formaldehyde, not to the molecule's backstory.
That mismatch is exactly why SHG catches people out:
- Formaldehyde-sensitive shoppers gravitate to "natural"/"clean" products — and SHG is one of the releasers most likely to be hiding there.
- It cross-reacts with the rest of the family (DMDM hydantoin, quaternium-15, imidazolidinyl/diazolidinyl urea, bronopol) and free formaldehyde.
- Because of its gentle reputation, it can be missing from avoidance lists — worth naming to your dermatologist directly.
This is the cleanest example of why "clean"/natural labels can't be trusted for formaldehyde avoidance. A product can be marketed as gentle and amino-acid-based while releasing the exact allergen you're trying to avoid. Read the ingredient list, not the front of the bottle.
How to spot and avoid it
- Read labels for Sodium Hydroxymethylglycinate (Suttocide A rarely appears on-pack).
- Don't trust "natural"/"clean" claims for formaldehyde avoidance.
- Avoid the whole releaser family if you're formaldehyde-sensitive.
- Prefer non-releaser preservation — phenoxyethanol, ethylhexylglycerin, or a genuinely non-releasing natural system (e.g. radish-root ferment).
When to see a dermatologist
A slow-building rash from lotions or "natural" products is worth patch testing — formaldehyde and several releasers are on standard series. If confirmed, name sodium hydroxymethylglycinate specifically so it isn't overlooked, and clear the full releaser family.
The bottom line
Sodium hydroxymethylglycinate is a formaldehyde releaser with a "natural" disguise. For most people it's an ordinary preservative; for the formaldehyde-allergic it's a genuine — and easily missed — trigger that hides precisely in the "clean" products they reach for. Judge it by the formaldehyde it releases, not its amino-acid origin.
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References & further reading
- Formaldehyde releasers in cosmetics — contact allergy review PubMed / Contact Dermatitis
- Formaldehyde-releasing preservatives — overview DermNet