Ingredient review
Quaternium-73
INCI: Quaternium-73
Quaternium-73 is a synthetic preservative booster that helps keep rinse-off products fresh, but it may cause irritation for sensitive skin types.
In plain English
Quaternium-73 is a man-made ingredient added to products like shampoos and body washes to help prevent germs and mold from growing. It works alongside other preservatives to keep the product safe to use over time. Because it's a quaternary ammonium compound (a type of positively charged molecule), it can sometimes be drying or irritating, especially for people with sensitive skin or eczema. It's mainly used in products that you rinse off, not leave on your skin.
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
Quaternium-73 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 Quaternium-73.
- 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
Quaternium-73 is a synthetic quaternary ammonium salt designed as an antimicrobial agent and preservative enhancer. It is not found in nature and is produced through chemical synthesis.
How it works
In a cosmetic product, Quaternium-73 disrupts the cell membranes of bacteria, yeast, and mold, preventing them from growing and spoiling the formula. It is often combined with other preservatives to reduce the overall preservative load needed.
Pros
Effective preservative booster
Helps keep rinse-off products free from harmful microbes, reducing the risk of contamination and spoilage.
Reduces need for harsher preservatives
When used in combination, it can allow formulators to use lower amounts of more irritating preservatives like parabens or formaldehyde releasers.
Cons and cautions
Potential skin irritation
As a quaternary ammonium compound, it can cause stinging, redness, or dryness, especially on sensitive or compromised skin.
Limited to rinse-off products
Its irritation potential means it is rarely used in leave-on products like moisturizers or serums, limiting its versatility.
Best for
- People with normal to oily skin who use rinse-off products
- Those looking for products with a broad-spectrum preservative system
Use caution if
- Individuals with sensitive, reactive, or eczema-prone skin
Usage tips
Safety summary
Quaternium-73 is considered safe for use in rinse-off cosmetics at low concentrations by major regulatory bodies. However, it can be a mild to moderate irritant for some individuals, particularly those with sensitive skin or skin conditions like eczema.
Research notes
Research on Quaternium-73 is limited compared to more common preservatives. Available studies confirm its antimicrobial efficacy against a range of bacteria and fungi. Human repeat insult patch tests indicate a low but present potential for skin sensitization.
Common label clues
- Typical concentration
- Typically used at 0.1% or less
- Regulatory status
- Approved for use in cosmetics in the EU, US, and many other regions, typically at concentrations up to 0.1% in rinse-off products.
- Common uses
- Shampoos, Body washes, Facial cleansers, Conditioners
- Environmental note
- As a synthetic quaternary ammonium compound, its environmental persistence and aquatic toxicity are areas of ongoing study; it is not biodegradable in all conditions.
Good to know
- Quaternium-73 is often listed near the end of the ingredient list due to its low use concentration.
- It is not related to vitamin B3 (niacinamide) despite the similar-sounding name.
Common questions
What is Quaternium-73 in beauty products?
Quaternium-73 is a man-made ingredient added to products like shampoos and body washes to help prevent germs and mold from growing. It works alongside other preservatives to keep the product safe to use over time. Because it's a quaternary ammonium compound (a type of positively charged molecule), it can sometimes be drying or irritating, especially for people with sensitive skin or eczema. It's mainly used in products that you rinse off, not leave on your skin.
What does Quaternium-73 do in a beauty product?
In a cosmetic product, Quaternium-73 disrupts the cell membranes of bacteria, yeast, and mold, preventing them from growing and spoiling the formula. It is often combined with other preservatives to reduce the overall preservative load needed.
Is Quaternium-73 safe for most people?
Quaternium-73 is considered safe for use in rinse-off cosmetics at low concentrations by major regulatory bodies. However, it can be a mild to moderate irritant for some individuals, particularly those with sensitive skin or skin conditions like eczema.
Who should be careful with Quaternium-73?
Individuals with sensitive, reactive, or eczema-prone skin
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.