Ingredient review

Quaternium-15

INCI: Quaternium-15

Quaternium-15 is an effective preservative but controversial due to its formaldehyde-releasing nature, which can cause skin irritation and allergic reactions in sensitive individuals.

beautyskincarepreservative

In plain English

Quaternium-15 is a synthetic preservative added to many water-based cosmetics to stop bacteria, mold, and yeast from growing. It works by slowly releasing tiny amounts of formaldehyde over time. Formaldehyde is a well-known preservative, but it can also be a skin irritant and allergen. Because of this, Quaternium-15 is considered safe at low levels by regulators, but it's often avoided in products for sensitive skin or in 'free-from' formulations.

Review score

Safety, usefulness, and evidence

2.5Fair
2.5/ 5

Higher-caution ingredient

The evidence base is relatively strong for its common cosmetic role.

Main practical flags: irritation is moderate; clogging risk is low.

Source
synthetic
Evidence
strong
Irritation
moderate
Clogging risk
low
How reviews are scored

Quick decision guide

Read the cautions before using

Quaternium-15 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.

  1. Step 1Start with the score, then check the irritation and clogging risk before judging Quaternium-15.
  2. Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
  3. 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

moderate

Can bother some users, especially with frequent use, damaged skin, or strong companion ingredients.

Clogging risk

low

Less likely to feel heavy or contribute to clogged pores for most skin types.

Evidence level

strong

There is a stronger practical or research basis for the ingredient role described here.

What it is

Quaternium-15 is a quaternary ammonium salt that acts as a preservative by slowly releasing formaldehyde. It is a white crystalline powder that is soluble in water.

How it works

When added to a product, Quaternium-15 breaks down over time to release formaldehyde. Formaldehyde then kills or inhibits the growth of microorganisms by cross-linking their proteins and DNA. This keeps the product safe from contamination during its shelf life.

Pros

Strong preservation

Effectively prevents bacteria, mold, and yeast growth, keeping products safe for months or years.

Cost-effective

Works at low concentrations, making it an inexpensive choice for mass-market formulations.

Cons and cautions

Formaldehyde release

Slowly releases formaldehyde, which can cause allergic reactions and skin irritation in sensitive people. The amount is regulated but still a concern for some.

Allergen potential

One of the more common causes of allergic contact dermatitis from preservatives, especially in leave-on products.

Best for

  • People without known formaldehyde allergies or sensitive skin
  • Those using rinse-off products like shampoos and body washes where exposure is brief

Use caution if

  • Individuals with a known allergy to formaldehyde or formaldehyde-releasing preservatives
  • People with eczema, rosacea, or very sensitive skin

Usage tips

Use in rinse-off products only if you have sensitive skin, to minimize contact time.
Check the full ingredient list if you have a known formaldehyde allergy, as other formaldehyde-releasing preservatives (like DMDM hydantoin) may also be present.
Store products containing Quaternium-15 in a cool, dry place to slow down formaldehyde release.

Safety summary

Quaternium-15 is considered safe for most people at regulated levels, but it is a moderate irritant and a common allergen due to its formaldehyde release. It is best avoided by those with sensitive skin or known allergies.

Research notes

Multiple studies confirm Quaternium-15 as a common cause of allergic contact dermatitis. Regulatory bodies have set safe use limits, but concerns about cumulative formaldehyde exposure persist. Evidence is strong for its allergenicity.

Common label clues

Typical concentration
Up to 0.2% (formaldehyde release is regulated)
Regulatory status
Approved for use in cosmetics in the US (FDA) and EU (SCCS) at concentrations up to 0.2%. Banned in leave-on products for children under 3 in the EU. Japan restricts its use.
Common uses
Shampoos, Conditioners, Body washes, Lotions, Makeup removers
Environmental note
Quaternium-15 is synthetic and not readily biodegradable. Its environmental impact is not well-studied, but formaldehyde release can be toxic to aquatic life at high concentrations.

Good to know

  • Quaternium-15 is often listed near the end of an ingredient list because it's used at low concentrations.
  • In the EU, Quaternium-15 is restricted to a maximum concentration of 0.2% and is banned in leave-on products intended for children under 3.
  • Many 'free-from' or 'clean beauty' brands avoid all formaldehyde-releasing preservatives.

Common questions

What is Quaternium-15 in beauty products?

Quaternium-15 is a synthetic preservative added to many water-based cosmetics to stop bacteria, mold, and yeast from growing. It works by slowly releasing tiny amounts of formaldehyde over time. Formaldehyde is a well-known preservative, but it can also be a skin irritant and allergen. Because of this, Quaternium-15 is considered safe at low levels by regulators, but it's often avoided in products for sensitive skin or in 'free-from' formulations.

What does Quaternium-15 do in a beauty product?

When added to a product, Quaternium-15 breaks down over time to release formaldehyde. Formaldehyde then kills or inhibits the growth of microorganisms by cross-linking their proteins and DNA. This keeps the product safe from contamination during its shelf life.

Is Quaternium-15 safe for most people?

Quaternium-15 is considered safe for most people at regulated levels, but it is a moderate irritant and a common allergen due to its formaldehyde release. It is best avoided by those with sensitive skin or known allergies.

Who should be careful with Quaternium-15?

Individuals with a known allergy to formaldehyde or formaldehyde-releasing preservatives People with eczema, rosacea, or very sensitive skin

Research sources

FDA: Cosmetics Safety Q&AOpenSCCS Opinion on Quaternium-15OpenPubMed: Allergic contact dermatitis from Quaternium-15Open

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.