Are sulfates as bad for your skin as they are made out to be? What’s the difference between SLS and SLES? Is Sodium Laureth Sulfate bad for skin? Should you be using sulfate-free cleansers?

In a world where people think all chemicals are ‘toxic’ and misinformation is rife, how do you work out which ingredients are bad for your skin and which are just misunderstood? Are sulfates always bad for skin?

The short answer?

No, sulfates are not universally bad for the skin.

Let’s have a look at why sulfates, such as Sodium Laureth Sulfate, get a bad reputation and why they may not be as bad for your skin as you think…

Table of Contents

What Are Sulfates & Why Are They Used In Cleansers?

Sulfates are anionic surfactants that are used in cleansers and other cosmetic products to produce a lather or foam ^[1]. Foam-based cleansers tend to be the best at removing dirt, oil, and other debris from the skin but, as a consequence, they may damage the skin’s barrier function and cause irritation.

Sodium lauryl sulfate (SLS) is probably one of the main reasons that sulfates have a bad reputation as it’s so good at damaging the skin’s barrier that it’s often used in research studies to purposely damage the skin in order to test whether moisturizers are able to repair that damage!

Sodium Laureth Sulfate, or Sodium Lauryl Ether Sulfate (SLES), is a gentler alternative to SLS that is less likely to cause irritation.

The Skin’s Barrier Function & Why It’s Important

The skin’s barrier function is performed and maintained by the outer-most layer of the skin, the stratum corneum, which keeps water in the skin and keeps irritants out.

The stratum corneum is said to have a ‘brick and mortar’ like structure, where skin cells (the bricks) are held together by a mixture of lipids (the mortar). The lipids (mostly ceramides, cholesterol, and fatty acids) play a vital role in regulating the water content of the skin. When the lipids are reduced within the stratum corneum, more water is able to escape leading to reduced skin hydration and more irritants are able to penetrate the skin and cause inflammation.

Why Do Sulfates Cause Irritation?

As mentioned earlier, sulfates are excellent at removing oil from the skin. However, this includes stripping the skin’s barrier of its natural oils.

When these lipids are removed, gaps are left between the cells in the skin’s barrier which allows water to escape and environmental pollutants to enter. This can lead to irritation and inflammation.

Are Sulfates Bad For Skin?

The degree of irritation caused by sulfates is dependent on the duration of exposure and the amount of the ingredient that penetrates the skin.

The latter is determined by a number of different factors such as the chemical properties of the ingredient, the way that it is applied, environmental factors (e.g. temperature and humidity), and the condition of the skin’s barrier ^[2].

Furthermore, skin irritation from SLS varies between individuals. For example, a number of research studies have found individual variations in the ‘irritation threshold’ of SLS – meaning the lowest concentration of SLS (%) required to cause visual skin inflammation after a 4-hour patch-test.

For some people, a concentration of less than 0.1% SLS was enough to cause visual skin irritation while others showed little irritation to SLS concentrations over 20% ^[2].

A key point to note here is that the various concentrations of SLS were applied to the skin, covered (as is the procedure for a patch-test), and then left on for 4 hours which is not reflective of how cleansers containing SLS or other sulfates would be used.

One reason that the irritation potential of SLS and other sulfates may vary between people may be due to the rate at which they penetrate the stratum corneum. Research has found that the thickness of the stratum corneum and the baseline rate of transepidermal water loss (TEWL) are highly predictive of how irritating a person is likely to find SLS ^[3].

In other words, if your skin is well hydrated and/or you have a thick stratum corneum, you are less likely to experience SLS-induced irritation.

Some sulfates also increase the skin penetration of other skincare products – making the products more effective. Increased effectiveness is usually considered a good thing. However, increasing the effectiveness of harsher actives (e.g. chemical exfoliants) may cause skin irritation.

Is Sodium Laureth Sulfate Bad For Skin?

Sodium Laureth Sulfate (SLES) is a much gentler alternative to SLS that is less likely to cause irritation. However, we have already established that SLS is not guaranteed to cause irritation for everyone and is, in fact, very useful for people with excessively oily skin.

For this reason, it’s misleading to suggest that sulfate-based cleansers are universally bad for the skin. In addition, just because a cleanser is ‘sulfate-free’ doesn’t mean that it won’t cause irritation. It’s more likely that this specific terminology has been added as a marketing tactic due to the fear surrounding sulfate-based cleansers.

Furthermore, irritation may be avoided altogether by moisturizing after the use of a sulfate-based cleanser.

Practical Tips

Here are some general tips to help reduce the likeliness of irritation from sulfate-based/foaming cleansers…

Foaming cleansers should only be used by those with oily skin and should ideally contain gentler alternatives to SLS, such as SLES.
It may be best to avoid cleansers that have SLS listed near the top of the ingredient list (i.e. cleansers with stronger concentrations of SLS).
Foaming cleansers should be avoided altogether by those with dry and/or sensitive skin.
Foaming cleansers are better suited to night-time only use as twice-daily use is more likely to cause irritation and oil and dirt build-up throughout the day.
If there is an ingredient that you know you’re are sensitive to (e.g. fragrance) avoid foaming cleansers that contain this as it may increase the irritation potential of said ingredient.
Use a barrier-repairing moisturizer after washing your face with a foam cleanser.
If you suffer from acne and are using a foam-cleanser alongside your other treatments and are not seeing any improvement, try switching to a gentle cream-based cleanser as your skin may be overproducing oil due to skin barrier damage/dehydrated skin.
Beware of assuming that a ‘sulfate-free’ cleanser will be less irritating than a sulfate-based cleanser as this is not always the case.
Finally, listen to your skin. You know your skin better than anyone and will have a good idea about whether it can tolerate sulfate-based cleansers or not.

References

Baumann, L. (2015). Cosmeceuticals and Cosmetic Ingredients. McGraw Hill: New York (USA). Information also available online here: https://www.mdedge.com/dermatology/article/151998/aesthetic-dermatology/recommending-efficacious-cleansers-your-patients
De Jongh, C., Verberk, M., Withagen, C., Jacobs, J., Rustemeyer, T., & Kezic, S. (2006). ‘Stratum corneum cytokines and skin irritation response to sodium lauryl sulfate’, Contact Dermatitis, 54(6), 325 – 333. Available at: https://www.researchgate.net/publication/6997622_Stratum_corneum_cytokines_and_skin_irritation_response_to_sodium_lauryl_sulfate
De Jongh, C., Jakasa, I., Verberk, M. & Kezic, S. (2006). ‘Variation in barrier impairment and inflammation of human skin as determined by sodium lauryl sulfate penetration rate’, British Journal of Dermatology, 154, 651-657. Available at: https://www.researchgate.net/publication/6997622_Stratum_corneum_cytokines_and_skin_irritation_response_to_sodium_lauryl_sulfate