Are Quaternary Ammonium Compounds Safe?

Would you like to know a secret I learned while reading numerous shampoo and conditioner labels?  It will help you choose the right shampoo and conditioner for your hair type without even trying them.  Here we go.  There is a group of chemicals that are very common in shampoos and conditioners but are rather controversial on the Internet.  Thus, chances are there is at least one of them in your shampoo or conditioner even if the products are marketed as natural or organic.  So, in this post, we will demystify the world of chemicals called quaternary ammonium compounds, or quats for short.

What are quaternary ammonium compounds?

To begin with, these ingredients perform several functions.  For example, some of them have antibacterial properties and are used as preservatives.  Others can serve as conditioners, antistatic agents, and viscosity control agents.

In hair products, they impart a “slippery” feeling to your hair, which helps you spread your conditioner better.  Consequently, combing is easier, and frizz is under control.  They also perform a coating function solving the problem of dry hair without flattening it.  In fact, they add volume to your hair.

In other words, if your hair is dry, frizzy, and thin and you can barely comb it, most likely your shampoo and conditioner have no quats.   

What are the most popular quats in hair products?

In the table below, you will see the most common quaternary ammonium compounds and some general facts about them.  Then, we will talk about each of them individually from the standpoint of scientific research on their safety.

Are quaternary ammonium compounds safe?

As you can see from the table, according to the EWG Skin deep database, most quats have limited safety data.  On the other hand, they are not on the 2020 CA Proposition 65 list of chemicals known to cause cancer or reproductive toxicity.  In addition, in its 2017 Allergen Series the American Contact Dermatitis Society lists none of them, except benzalkonium chloride, as core allergens.   

Alternatively, the European Chemicals Agency (ECHA) emphasizes their toxicity to aquatic life and harmful effects on the organs.  However, the ECHA does not specify the concentrations of these ingredients that may cause the harm described.  So, let us look at other scientific sources to find this information about each of these ingredients.

Guar hydroxypropyltrimonium chloride

To start with, it belongs to a group of galactomannans, which are legume polysaccharides.  It is a quaternary ammonium derivative of guar (aka cluster beans) that undergoes conversion with 3-chloro-2 hydroxypropyl trimethyl ammonium chloride.  So, while it is plant-derived, there is a synthetic portion to it. 

Unlike other quats with limited data, the Skin Deep database rates guar hydroxypropyltrimonium chloride 1.  Nevertheless, it puts it on the EWG’s restricted list of ingredients, which means that they may be acceptable after their verification process.  

According to the 2015 Cosmetic Ingredient Review report, it is used in leave-on products in concentrations of 0.005-2% and in rinse-off products in concentrations of 0.02-2%.  While the CIR Expert Panel found this representative of quaternary ammonium compounds not genotoxic, it acknowledged some data gaps.  Thus, there is no data on its reproductive toxicity, carcinogenicity, dermal irritation or sensitization.  

However, the Panel determined that the available data about other polysaccharides or their derivatives, used for cosmetic purposes, could support the safety of the entire group.  Thus, a hair styling product containing 2% hydroxylpropyl guar yielded negative results for skin irritation and sensitization.  

Additionally, the Panel noted that galactomannans are unlikely to be absorbed systemically due to the large size of the molecules.  In sum, the Panel considers guar hydroxypropyltrimonium chloride safe in present usage and concentrations (up to 2%).

Behentrimonium methosulfate

As a quaternary ammonium salt, this quat is a polymer derivative of the group of trimoniums.  The Skin Deep database used to rate it 1, but now it rates behentrimonium methosulfate 3-4.  Moreover, it puts it on the EWG’s unacceptable list of ingredients because they believe it may trigger asthma and be toxic to human reproductive system. 

The EWG cites a study in the reproductive toxicology journal that describes decreased reproductive performance in laboratory mice.  It coincided with the introduction of a disinfectant containing both alkyl dimethyl benzyl ammonium chloride (aka benzalkolnium chloride) and didecyl dimethyl ammonium chloride (aka didecyldimonium chloride).  However, there was no mentioning of behentrimonium methosulfate in the study.  Neither have I found any reproductive toxicity concern for behentrimonium methosulfate anywhere else in scientific literature. 

According to the 2012 CIR Safety Assessment of Trimoniums in Cosmetics, this kind of quaternary ammonium compounds is currently used at 0.0005% to 10% in rinse-off and at 0.001% to 4% in leave-on products.  Further, the CIR states that the available data on many of the trimoniums are sufficient to support the safety of the entire group.  Thus, due to the lack of dermal penetration, there appears to be no genotoxic risk from the use of trimoniums in cosmetics. 

In addition, the CIR states that the literature lacks clinical reports of irritation and/or sensitization involving trimonium compounds.  Hence, the CIR Expert Panel concludes that behentrimonium methosulfate is safe in the present practices of use and concentration when formulated to be nonirritating.

Behentrimonium chloride

Just like behentrimonium methosulfate, behentrimonium chloride is another type of quaternary ammonium compounds from the group of trimoniums.  The Skin Deep database also rates behentrimonium chloride 3-4 and puts it on the EWG’s unacceptable list of ingredients for the same reason.  They think, it may trigger asthma and be toxic to the human reproductive system and cite the study in the reproductive toxicology journal.  Yet, the study does not mention behentrimonium chloride, only benzalkolnium chloride and didecyldimonium chloride.  And I found no reproductive toxicity concern for behentrimonium chloride in other sources. 

According to the European Scientific Committee on Consumer Safety (SCCS) report, rinse-off hair products can safely use it in concentrations up to 5.0% and leave-on hair and facial products up to 3.0%.  Unlike some other quats, it causes neither immediate dermal irritation nor delayed sensitization in a concentration >5% (source).

Next, the 2012 CIR report underlines that current rinse-off products use behentrimonium chloride at concentrations of 0.0005% to 10% and leave-on products at 0.001% to 4%.  The EU restricted its use as a preservative to 1%.  It may cause mild eye irritation at 3% and mild to severe eye irritation at 10%.  However, all the eye products containing trimonium ingredients use 0.3% or less, well below these concentrations.                                                                          

Further, human dermal irritation studies yielded no irritation at 5.0% and no sensitization at 2.4%.  It is not mutagenic, either.  Therefore, the CIR Panel concluded that it is safe in present practices of use and concentration in nonirritating formulations.

Cetrimonium chloride

As it follows from its name, cetrimonium chloride is a trimonium type of quaternary ammonium compounds.  Just as behentrimonium chloride, it can function as a preservative.  The Skin Deep database rates cetrimonium chloride 3-4 with fair data.  It also adds it to the EWG’s unacceptable list as toxic to the human reproductive system and an asthma trigger.  As with behentrimonium methosulfate and behentrimonium chloride, the EWG cites the study that in my opinion does not include cetrimonium chloride, only benzalkolnium chloride and didecyldimonium chloride.

According to the European SCCS report, this member of the quats family is safe in rinse-off hair products up to 2.5% and leave-on products up to 1.0%.  Additionally, it is safe in leave-on facial creams at up to 0.5%.  

In the meantime, the 2012 CIR report states its current use in cosmetic products in concentrations between 0.0008% and 10%.  Just like behentrimonium chloride, the EU restricts it to 1% as a preservative.  Although it may cause eye irritation at concentrations of 2% and above, all the eye products use 0.3% or less of trimonium ingredients, well below these concentrations.

Further, in human studies, cetrimonium chloride was not an irritant in concentrations up to 1%.  But there were mixed results (nonirritant-slight-moderate) in concentrations above 1%.  Moreover, there was no evidence of birth defects at 2.0% concentration.  Besides, it is not sensitizing at 0.25%, and not mutagenic.  Thus, the Panel concluded that it is safe in the present practices of use and concentration when formulated to be nonirritating.

Stearalkonium chloride – one of the most popular quaternary ammonium compounds in shampoos and conditioners

First, stearalkonium chloride can also serve as a preservative and has a rating of 5 in the Skin Deep database.  Just as the other quats we talked about above, the EWG includes it in the unacceptable list of ingredients because they believe that it may trigger asthma and may be toxic to human reproductive health.  As with the above quaternary ammonium chemicals, the EWG cites the study in which I do not see stearalkonium chloride.

Second, the European SCCS considers it safe in rinse-off hair care products up to 2.5% and leave-on hair care products up to 1.0%.  And in the leave-on facial cream products, it is safe up to 0.5%.  Also, the SCCS does not state any reproductive toxicity effects.  Thus, in animal studies, stearalkonium chloride did not show any harm to offspring even after exposure to big doses.

Finally, in 1982 the Cosmetic Ingredient Review Expert Panel concluded that stearalkonium chloride was not a sensitizer or an irritant in concentration currently used in personal care products.  Then, in 2003, the Panel reviewed the safety data and decided not to re-open the report. 

Admittedly, there was a data gap regarding carcinogenic, mutagenic, or teratogenic effects of stearalkonium chloride.  Therefore, the Panel could not make a conclusion about its safety in those areas.  Nevertheless, I have not found any health concerns in medical literature.  And as you see in the table, the American Contact Dermatitis Society does not list it as an allergen.

Benzalkonium chloride

The last member of the quaternary ammonium compounds family in this post is benzalkonium chloride.

The EWG also rates it 5, but lists it among the EWG’s restricted ingredients.  A common preservative, it links to skin irritation and can act as a sensitizer causing an allergic reaction over time (source).  Also, this study describes decreased fertility in mice, even when the researchers used benzalkonium chloride (chemical name is alkyl dimethylbenzyl ammonium chloride) just to clean their cages.  (This is the study the EWG cites for reproductive toxicity concern for all the quats except guar hydroxypropyltrimonium chloride.)

On the other hand, the 2006 CIR report deemed it safe in concentrations up to 0.1% as a free active ingredient.  In 2006, 89 products contained it at concentrations between 0.01% and 0.5%.  Even with data gaps, the Panel assessed its safety using the overall information available on the products with benzalkonium chloride and its concentrations.  

Thus, the Panel noted that it can increase the dermal penetration of other chemicals (e.g., betamethasone phosphate).  Therefore, the Panel advised formulators to consider this factor in their product formulations.  

I highly recommend avoiding benzalkonium chloride.  Also, I recommend avoiding grapefruit seed extract, because it may contain benzalkonium chloride as a hidden ingredient.  If you use WaterWipes baby wipes, you might want to read my post about them.  When I first contacted the company, they claimed that their wipes contained water and pure grapefruit seed extract only.  Later, it turned out to be a different story.

Conclusion about the quaternary ammonium compounds safety

In an ideal world, it is best to avoid quats, especially if you do not need them.  Nevertheless,  sometimes, you can find them even in baby washes.  To be on the safe side, I recommend not using them on your baby, especially if she has little hair.  I have used only plain soap on my son since his birth, and his hair looks shiny, hydrated, and healthy.

The good news is that some companies do not include quats.  Recently, Pure Haven replaced behentrimonium methosulfate with eco-friendly conditioning ingredients – brassica alcohol, brassicyl valinate esylate, and heptyl undecylenate.  True Botanicals and Wellnesse haircare products have them, too. 

However, quat-free products may not work well for people with colored, damaged, dry, or curly hair.  That might be the reason that some people do not like natural shampoos.

On the other hand, I believe quaternary ammonium ingredients are not as bad as the EWG views them.  After hours of research, I still do not see how the EWG decided that all quaternary ammonium chemicals are a subject of reproductive toxicity concern.  In addition, many other products have even worse ingredients: formaldehyde releasing preservatives, parabens, methylisothiazolinone or fragrance.  You can read about DevaCurl facing lawsuits from people who claim to have been injured from their products.  In other words, except benzalkonium chloride, I am okay with quaternary ammonium compounds when you use them knowingly.  

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