Are Quaternary Ammonium Compounds (Quats) Safe? A Guide To The 7 Most Common Quats

If you have ever flipped over a bottle of conditioner and found a tongue-twister like Behentrimonium Methosulfate or Cetrimonium Chloride in the ingredient list, you have met a quat. Quaternary ammonium compounds — “quats” for short — are most common in hair care. They are also some of the most misunderstood.

In this guide, I will explain what quats actually are and where they are found as well as give you my up-to-date rating for each of the seven quats you are likely to see on a label.

Let’s demystify them together.

What Are Quaternary Ammonium Compounds (Quats)?

Quaternary ammonium compounds are a family of positively charged (cationic) molecules built around a central nitrogen atom. That positive charge is the whole story: hair is slightly negatively charged, especially when it is damaged, so quats are drawn to it and cling to the surface. That is what gives conditioner its “slippery” feel.

In cosmetic chemistry and in the cosmetology world, quats are valued as conditioning agents and antistatic agents. A few are also used as preservatives, and one (Benzalkonium Chloride) – as a disinfectant.

If you are skimming a label, most quats are easy to spot. They tend to end in -onium chloride or –onium methosulfate.

What Do Quats Do In Your Products?

Quats earn their place on the ingredient list because they solve several problems at once:

• Conditioning and slip: They coat the hair shaft so your conditioner spreads easily and combing is smoother.
• Frizz and static control: The cationic charge neutralizes the static that makes hair fly away.
• Volume without heaviness: They smooth dry hair without flattening it, which is why quat-free products sometimes feel less “finished.”
• Preservation: Some quats can function as preservatives to slow microbial growth. That is useful, but it is one reason I prefer them in rinse-off products rather than leave-on ones.
• Emulsifying: In creams and lotions, quats help keep oil and water blended so the product stays smooth.
• Disinfecting: Benzalkonium Chloride is strong enough to kill germs, which is why it shows up in sanitizing products rather than only in conditioners.

What Common Products Contain Quats?

You will find quats in:

• conditioners and 2-in-1 shampoos
• leave-in conditioners, detanglers, and curl creams
• baby washes and baby wipes
• facial creams and lotions
• disinfectants and sanitizing wipes

List Of Quats And How Safe Each One Is

Here is how each of the seven quats lands on my four-tier ingredient rating system, from most to least preferred.

Want all 7 quats in one glance? Grab my free, printable Quats Safety Pocket Guide — the whole comparison on a single page!

Behentrimonium Chloride — Better (Limited Use)

Behentrimonium Chloride is made with methyl chloride, which is not classified as a carcinogen. Plus, is too large and too charged to penetrate skin. It is not a recognized contact allergen. Because it is also an EU-approved preservative, I keep it to rinse-off conditioners rather than leave-on products. Of the conditioning quats, it is one of the cleanest. Full breakdown: Is Behentrimonium Chloride Safe?

Cetrimonium Chloride — Better (Limited Use)

Cetrimonium Chloride is chemically very close to Behentrimonium Chloride, but its weak spot is irritation at higher amounts. At the low levels used in conditioners it is gentle, does not penetrate skin, and is not an allergen. A solid rinse-off ingredient. See my complete review: Is Cetrimonium Chloride Safe?

Steartrimonium Chloride — Better (Limited Use)

Steartrimonium Chloride shares the same friendly chemistry (methyl chloride, no skin penetration, dermal reproductive studies negative) with Behentrimonium and Cetrimonium Chloride. It does have irritation potential in a concentrated form, though. At in-use levels it is a reasonable rinse-off conditioner. Get the details: Is Steartrimonium Chloride Safe?

Guar Hydroxypropyltrimonium Chloride — Better (Limited Use)

Guar Hydroxypropyltrimonium Chloride is a cationic conditioning polymer derived from guar (the same plant behind guar gum). It is enormous (molecular weight over 50,000), so it cannot be absorbed, and it is very gentle on skin. The cosmetic-grade ingredient is not a known allergen. My only reservation is a residual processing chemical (CHPTAC) the EU flags as a suspected carcinogen. More on this one: Is Guar Hydroxypropyltrimonium Chloride Safe?

Behentrimonium Methosulfate — Better (Not In My Top Picks)

Behentrimonium methosulfate is a gentle, non-irritating conditioner that behaves much like its chloride cousins. But it is manufactured using dimethyl sulfate, which IARC classifies as 2A (probably carcinogenic). The finished ingredient does not penetrate skin, and I have found no credible reproductive-toxicity signal for it specifically. Yet, because gentler options that skip that starting material exist, it stays out of my top picks. Dig into the evidence: Is Behentrimonium Methosulfate Safe?

Stearalkonium Chloride — Better (Not In My Top Picks)

Stearalkonium Chloride is made with benzyl chloride classified by IARC as 2A (probably carcinogenic). At in-use levels it is not an irritant or a listed allergen, but it can form nitrosamines if a product also contains a nitrosating preservative. The full story: Is Stearalkonium Chloride Safe?

Benzalkonium Chloride — Not A Fan

Benzalkonium chloride is a recognized contact allergen and asthma trigger, and it can irritate skin and eyes even at 0.1%. While it does not penetrate skin itself, it boosts the penetration of other ingredients, including potentially harmful ones. It is not classified as an endocrine disruptor, but animal studies have raised fertility signals at high exposures (in mice and in medaka fish). I recommend avoiding it.

One related tip: I also recommend being cautious with Grapefruit Seed Extract because it can contain benzalkonium chloride as an undisclosed ingredient in baby wipes. Please read about my research into WaterWipes Baby Wipes to find out more about this hidden ingredient. Read my deep dive: Is Benzalkonium Chloride Safe?

Quats Vs. Formaldehyde-Releasing Preservatives: A Common Mix-Up

A lot of confusion online comes from mixing up two very different ingredient families that happen to share part of a name. The conditioning quats in this guide are not the same as quaternium-15, a formaldehyde-releasing preservative. The naming overlap is unfortunate, but none of the seven quats above release formaldehyde.

If a dermatologist has flagged “quats” in connection with a formaldehyde allergy, it is worth asking exactly which ingredient they mean (it is most likely quaternium-15, not the “quats”). If you want to steer clear of the real formaldehyde releasers, my guide on how to protect yourself from formaldehyde in products shows you how to spot and avoid them.

Can You Find Quat-Free Products?

Yes, and quat-free hair care products can work beautifully. For instance, the shampoo and conditioner I use (and love!) are completely quat-free and do a wonderful job on my hair adding volume and promoting new growth. Instead of conditioning quats, they rely on newer plant-based ingredients like:

• brassica alcohol
• brassicyl valinate esylate
• heptyl undecylenate.

So, if you would rather skip quats altogether, you have genuinely good options. And if you do choose a rinse-off conditioner with a “Better (Limited Use)” quat, that can be a perfectly reasonable choice too — especially for colored, damaged, dry, or curly hair. The goal is always an informed choice, not fear.

Are Quaternary Ammonium Compounds Safe? My Overall Take

Here is the short version. Quats are not all the same. Some are acceptable in my top rinse-off products, a couple are not in my top picks, and one I recommend avoiding.

Two simple ideas guide my ratings.

First, where the product goes. A rinse-off conditioner washes away in a minute. A leave-on product stays on your skin all day. Behentrimonium Chloride, Cetrimonium Chloride, and Steartrimonium Chloride double as germ-fighting preservatives, so I would prefer them in rinse-off products, not leave-on ones.

Second, what the quat is made from. Stearalkonium Chloride, Behentrimonium Methosulfate, and Benzalkonium Chloride are each made using a chemical classified as probably carcinogenic, and Guar Hydroxypropyltrimonium Chloride is made with a chemical the EU calls a suspected carcinogen. The finished ingredients are large and do not soak into skin, so this is not a cause for panic. But when I have a gentler choice, I take it.

So here is how it shakes out:

• Better (Limited Use): Behentrimonium Chloride, Cetrimonium Chloride, Steartrimonium Chloride, and Guar Hydroxypropyltrimonium Chloride
• Better (Not In My Top Picks): Behentrimonium Methosulfate and Stearalkonium Chloride
• Not A Fan: Benzalkonium Chloride

Quats are not the villains the internet makes them out to be. Read the label, choose rinse-off when you can, and skip Benzalkonium Chloride.

Frequently Asked Questions

Is Quaternary Ammonium Safe?

It depends on which one and its use. Most conditioning quats are reasonable in rinse-off products; benzalkonium chloride is the one I recommend avoiding. See the comparison table above for my rating of each.

Does Behentrimonium Methosulfate Cause Cancer?

The finished Behentrimonium Methosulfate ingredient is not classified as a carcinogen and does not penetrate skin. My reservation is that it is made using dimethyl sulfate, an IARC 2A chemical, which is why I rate it Better (Not In My Top Picks) rather than recommending it.

What Products Contain Quats?

The products that contain quats are mostly conditioners, leave-in treatments, shampoos, baby wipes and washes, some facial lotions, and — for Benzalkonium Chloride — disinfectants and sanitizing wipes.

What Does “Quat-Free” Mean?

“Quat-free” means a product contains none of the quaternary ammonium conditioning or preservative ingredients. Pure Haven is one example of a quat-free line.

Are Quats The Same As Formaldehyde Releasers?

No, quats are not the same as formaldehyde releasers. The conditioning quats in this guide do not release formaldehyde. The mix-up usually comes from quaternium-15, a separate formaldehyde-releasing preservative.