What Is Quaternium-15?
In plain English: Quaternium-15 is a synthetic preservative that acts as a formaldehyde releaser, giving off small amounts of formaldehyde to prevent microbial growth in water-based products. It is one of the more common causes of allergic contact dermatitis on the hands.
Also listed as: quaternium-15, Dowicil 200, methenamine 3-chloroallylochloride, formaldehyde-releasing preservative
The honest science
Quaternium-15 is a quaternary ammonium salt used specifically as a preservative. It works as an antimicrobial by slowly releasing formaldehyde, especially at lower pH, which keeps water-based formulas from spoiling 12.
Among preservatives, quaternium-15 is a notable allergen. It has been reported as one of the single most common causes of allergic contact dermatitis on the hands, and it ranked among the most prevalent allergens in patch-test surveys 2. Many people allergic to quaternium-15 also react to formaldehyde, though some have a specific sensitivity to the ingredient itself 12.
To keep it honest: the documented risk is allergic and irritant contact dermatitis, an itchy rash in sensitized people, rather than acute toxicity at the small amounts used to preserve products. Because it is a formaldehyde releaser, people with a formaldehyde allergy or those who simply prefer to avoid formaldehyde exposure often choose to skip it 1. Its use has declined in many US and European products as awareness of the allergy has grown 2.
Where you'll find it
- all-purpose cleaners
- liquid soaps and detergents
- cosmetics and lotions
- shampoos
- wet wipes
The safer-swap angle: If formaldehyde releasers are on your avoid list, plant-based formulas make it simple. Ecolosophy's small-batch concentrate is made with care and contains no quaternium-15 or other formaldehyde releasers.
Frequently asked questions
Is quaternium-15 a formaldehyde releaser?
Yes. It slowly releases formaldehyde as its preservative mechanism, particularly in more acidic formulas. That is why people with a formaldehyde allergy often react to it.
Is quaternium-15 a quat disinfectant?
Despite the name, it is used as a preservative, not as a surface disinfectant like benzalkonium chloride. It is chemically a quaternary ammonium salt but serves a different job.
How do I know if I am reacting to it?
Persistent itchy, red hand dermatitis after using a product is a common sign. A dermatologist can confirm with patch testing. Switching to products without formaldehyde releasers often helps.
Sources
- Quaternium-15 — Wikipedia
- Quaternium-15 contact allergy — DermNet NZ
Ingredient safety data changes as new research is published, and product formulas change over time. Always read the current label and check primary sources.
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