Ingredient review
Sodium Hydroxymethylglycinate
INCI: Sodium Hydroxymethylglycinate
A synthetic preservative that helps keep products fresh but may cause irritation for sensitive skin.
In plain English
Sodium hydroxymethylglycinate is a man-made ingredient added to cosmetics to stop bacteria, yeast, and mold from growing. It works by releasing a tiny amount of formaldehyde over time, which acts as a preservative. While it's effective at keeping products safe, the formaldehyde release can be irritating for some people, especially those with sensitive or allergy-prone skin. It's commonly found in rinse-off products like cleansers and shampoos, but also appears in some leave-on formulas.
Review score
Safety, usefulness, and evidence
Potentially useful with some tradeoffs
The evidence base is useful, but some claims depend heavily on the formula.
Main practical flags: irritation is moderate; clogging risk is low.
- Source
- synthetic
- Evidence
- moderate
- Irritation
- moderate
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Sodium Hydroxymethylglycinate can be useful, but watch for some irritation potential.
Plain-English read
Treat this as a practical screening step before you compare products that contain this ingredient.
- Step 1Start with the score, then check the irritation and clogging risk before judging Sodium Hydroxymethylglycinate.
- Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
- Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.
Score terms in plain English
Irritation risk
moderateCan bother some users, especially with frequent use, damaged skin, or strong companion ingredients.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
moderateThere is useful support, but formula details and claim strength still matter.
What it is
Sodium hydroxymethylglycinate is a synthetic preservative that belongs to the formaldehyde-releasing preservative family. It is created by reacting glycine (an amino acid) with formaldehyde, and it slowly releases small amounts of formaldehyde to prevent microbial contamination.
How it works
In a cosmetic product, sodium hydroxymethylglycinate gradually breaks down to release formaldehyde, which is a potent antimicrobial agent. This formaldehyde kills or inhibits the growth of bacteria, yeast, and mold, extending the product's shelf life and keeping it safe to use over time.
Pros
Effective preservation
Sodium hydroxymethylglycinate provides broad-spectrum protection against bacteria, yeast, and mold, helping products stay fresh longer.
Low cost
It is an inexpensive preservative option, making it common in budget-friendly and mass-market cosmetics.
Cons and cautions
Formaldehyde release
This ingredient slowly releases formaldehyde, which can be irritating and is a known allergen for some people.
Irritation potential
Even at approved levels, it may cause stinging, redness, or contact dermatitis, especially on sensitive or damaged skin.
Best for
- People with normal to oily skin who use rinse-off products
- Those looking for an affordable preservative system
Use caution if
- Individuals with sensitive, reactive, or eczema-prone skin
- Anyone with a known formaldehyde allergy or sensitivity
Usage tips
Safety summary
Sodium hydroxymethylglycinate is considered safe for use in cosmetics at regulated concentrations, but its formaldehyde-releasing nature means it can cause irritation or allergic reactions in sensitive individuals. It is best suited for rinse-off products and should be avoided by those with known formaldehyde allergies.
Research notes
Research confirms that sodium hydroxymethylglycinate is an effective antimicrobial preservative. Studies also show that it can cause contact dermatitis in a subset of the population, particularly those with formaldehyde sensitivity. Regulatory bodies like the Cosmetic Ingredient Review (CIR) have deemed it safe within specified limits.
Common label clues
- Typical concentration
- 0.1% to 1%
- Regulatory status
- Approved for use in cosmetics in the US, EU, and many other regions, with concentration limits typically capped at 0.5% to 1% depending on product type.
- Common uses
- Cleansers, Shampoos, Conditioners, Body washes, Leave-on products
- Environmental note
- Formaldehyde-releasing preservatives can be persistent in water systems, but sodium hydroxymethylglycinate is generally considered biodegradable at low concentrations.
Good to know
- Sodium hydroxymethylglycinate is often listed near the end of ingredient lists due to low use concentrations.
- It is sometimes used in combination with other preservatives to reduce overall irritation potential.
- The formaldehyde release is regulated to stay within safe limits, but cumulative exposure from multiple products can be a concern.
Common questions
What is Sodium Hydroxymethylglycinate in beauty products?
Sodium hydroxymethylglycinate is a man-made ingredient added to cosmetics to stop bacteria, yeast, and mold from growing. It works by releasing a tiny amount of formaldehyde over time, which acts as a preservative. While it's effective at keeping products safe, the formaldehyde release can be irritating for some people, especially those with sensitive or allergy-prone skin. It's commonly found in rinse-off products like cleansers and shampoos, but also appears in some leave-on formulas.
What does Sodium Hydroxymethylglycinate do in a beauty product?
In a cosmetic product, sodium hydroxymethylglycinate gradually breaks down to release formaldehyde, which is a potent antimicrobial agent. This formaldehyde kills or inhibits the growth of bacteria, yeast, and mold, extending the product's shelf life and keeping it safe to use over time.
Is Sodium Hydroxymethylglycinate safe for most people?
Sodium hydroxymethylglycinate is considered safe for use in cosmetics at regulated concentrations, but its formaldehyde-releasing nature means it can cause irritation or allergic reactions in sensitive individuals. It is best suited for rinse-off products and should be avoided by those with known formaldehyde allergies.
Who should be careful with Sodium Hydroxymethylglycinate?
Individuals with sensitive, reactive, or eczema-prone skin Anyone with a known formaldehyde allergy or sensitivity
Research sources
Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.