Is this a natural preservative?

It is derived from glycine, an amino acid. That describes where it comes from, not what it does — in the product it releases formaldehyde, exactly as the older releasers do.

So it is the same as DMDM hydantoin?

Not the same molecule, but the same mechanism and the same relevance to a formaldehyde allergy. They differ in the chemistry around the release and in how they are marketed.

Why does it appear in clean-beauty products?

Because the name does not read as alarming and its glycine origin fits a natural-derived story. That is a positioning decision rather than a chemical distinction.

I react to formaldehyde. Can I use it?

If a patch test has named formaldehyde or a releaser, treat this as one of them and take the question to a dermatologist rather than deciding from the ingredient list alone.

Should I look for a product without any preservative instead?

Only if it contains no water. A water-based product with no preservative system is not a safer product; it is an unprotected one.

Sodium Hydroxymethylglycinate — Ingredient Guide

How it works

It is built from glycine, the smallest amino acid, and that ancestry is most of its marketing. In a formula it behaves like the older formaldehyde releasers: the molecule gives up small amounts of formaldehyde into the water phase, and that is what holds bacteria back. The naming and the sourcing story differ from DMDM hydantoin; the mechanism does not.

Like every preservative it is pH-dependent, and a formulator chooses it against the pH of the finished product rather than dropping it into anything. It is also usually part of a system rather than the whole of one, since a single preservative rarely covers bacteria, yeast and mould equally well.

The evidence

Its preservative performance is established and it has been in commercial use for a long time. The interesting part is the gap between how it is presented and what it does.

Because it is glycine-derived and reads as unfamiliar rather than alarming, it turns up in products positioned as natural, gentle or free-from — sometimes in the same catalogue that lists formaldehyde releasers as things to avoid. Anyone genuinely sensitised to formaldehyde needs to recognise this name, and the label will not help them: nothing on the front of the pack distinguishes it from a preservative with no formaldehyde chemistry at all.

Regulatory status is the other moving part. Permitted-preservative lists differ between markets, they are revised, and formaldehyde-releasing preservatives as a class have been under review in more than one jurisdiction. The current rule where you live is the one that matters, and it may not be the one a blog post quoted three years ago.

Suitability

Fine for most people at preservative levels
Avoid on a known formaldehyde or formaldehyde-releaser allergy
Being derived from an amino acid says nothing about how it works or how you will react to it
Its presence is not a mark against a formula — an unpreserved water-based product is the worse option

Concentration

No figure is quoted. Maximum permitted levels are set in regulation, differ by market and change; the honest instruction is to check the rule that applies where the product is sold rather than to trust a number copied from memory. As with any preservative it is used at fractions of a percent, so its position near the end of an ingredient list tells you nothing unusual.

Conflicts & combinations

No notable incompatibility with common actives. It is generally combined with other preservatives to cover the full range of organisms, and with a chelating agent, which ties up the metal ions microbes rely on and makes the system harder to overcome. The practical combination to think about is not chemical: if you are avoiding formaldehyde releasers, this one and the urea-derived preservatives belong on the same list, and a product can contain more than one of them.