SLS and SLES — what are they and should you avoid them?
SLS and SLES under the microscope: what sulfates in cosmetics are, when they can be a problem and how to choose gentler formulas wisely.
The abbreviations SLS and SLES are very familiar to anyone trying to choose gentler cleansing products. The trouble is that a lot of oversimplification has built up around these names. Online you'll often read that "sulfates destroy your skin" or that any product containing SLS should be rejected outright. In practice, though, what matters is not just the presence of a particular detergent, but the whole formula, how often you use it and how your individual skin reacts.
It's worth knowing that detergents are necessary, because they're what removes sebum, dirt and product residue. Without them, a shampoo, shower gel or cleansing paste simply wouldn't do their job. So the question isn't "is this detergent bad?" but "is this particular detergent, in this formula, right for my skin and hair?". If you want to compare products by their composition, our ingredient descriptions and filters such as Sulfate-free will come in handy.
What do SLS and SLES mean?
SLS stands for sodium lauryl sulfate, and SLES for sodium laureth sulfate. Both belong to the group of anionic detergents, that is, cleansing agents responsible for washing and foam. Their presence in cosmetics is no accident: they're effective, well understood by formulators and predictable to work with. That's precisely why they show up so often in shampoos, shower gels and cleansing products.
Despite their similar names, they're not identical ingredients. In practice, SLES is often seen as gentler than SLS, although it can still be problematic for people with a particularly sensitive or compromised hydrolipidic barrier. Even so, the mere presence of one of these detergents doesn't tell you everything about how comfortable a product will be to use.
Why do sulfates stir up so much emotion?
Because they work effectively, and effective cleansing is often felt as "strength". A product with sulfates usually foams well, gives a sense of thorough cleansing and quickly removes excess sebum. For some people that's an advantage, but for others it leads to a feeling of tightness, roughness or faster irritation. It's these experiences that give rise to negative opinions.
However, two situations need to be distinguished. One is care that is objectively too harsh for sensitive skin. The other is the automatic assumption that every product with SLS or SLES is bad by definition. That conclusion goes too far, because a lot depends on the dose, the presence of soothing agents and whether a given product is rinsed off after a few dozen seconds or left on the skin.
When is it worth avoiding SLS and SLES?
If you have a scalp prone to irritation, atopic conditions, itching or dryness, or colour-treated hair that quickly loses comfort after washing, a gentler cleansing base is often the more sensible choice. The same goes for frequent washing of hair and face. The more often a product comes into contact with the skin's protective barrier, the more important the gentleness of the formula becomes.
In such cases the Sulfate-free filter can make selection much easier. It's still worth checking other elements of the composition, though: fragrance, alcohol, preservatives, the presence of soothing agents and whether the product contains an unusually high number of potentially irritating ingredients.
When can sulfates be a good fit?
For people whose scalp tends to get oily quickly, when occasionally using more deeply cleansing shampoos, or when you need to remove built-up silicones and styling products, sulfates can be a practical tool. Not every routine has to rely solely on the gentlest detergents. Sometimes you simply need stronger cleansing done deliberately and not too often.
This is an important point, because demonizing every detergent with higher cleansing power can lead to the opposite problem: an under-cleansed scalp, discomfort and poorer tolerance of other products. The best routine usually isn't about extremes, but about matching the product to a specific goal.
How to read the label beyond SLS and SLES?
If you see SLS or SLES near the top of the ingredient list, look straight at the rest of the formula. Are there gentle secondary surfactants? Are there humectants, glycerin, panthenol, betaine or ingredients that support skin comfort? Is the fragrance composition extensive? Is the product meant to be used daily or occasionally? Only a complete analysis makes sense.
It also helps to compare several products in the same category. On PurScore you can line up compositions and check whether a product relies solely on stronger detergents or whether the manufacturer has built a more balanced formula. A good starting point is our composition assessment methodology and the INCI dictionary.
Myth: "If a product foams, it's definitely harmful"
Abundant foam is not, in itself, proof that a cosmetic is dangerous. Foam affects the sensory experience more than it offers an automatic safety verdict. Sometimes a product with rich foam is well tolerated, while a product that foams less doesn't have to be ideal for every skin. That's why it's not worth using the feel of washing as your main criterion.
Likewise, the "SLS/SLES-free" label doesn't automatically mean a gentle product. You still need to check the rest of the composition and the product's function. For an informed choice, comparing formulas is much better than judging packaging by a single marketing slogan.
The practical takeaway
SLS and SLES are not "ingredients banned for everyone", but detergents that you need to place in the context of your whole care routine. For some they'll be too strong, while for others they'll prove useful in specific situations. The most important thing is to know what your skin needs and how often you use a given product.
If gentler cleansing matters to you, use the filters, compare compositions and don't stop at the front of the packaging. Take a look at our ingredient database, check products with the Sulfate-free filter and choose a formula that makes sense in practice.
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FAQ
No. They are two different anionic detergents. Both cleanse, but they aren't identical in terms of structure or how they feel on the skin.
No. People with sensitive, dry or reactive skin more often prefer gentler formulas, but that doesn't mean sulfates are unsuitable for everyone.
No. Gentleness is determined by the entire formula, not just the absence of one or two detergents.
For example, for deeper cleansing, removing built-up styling products, or for people who want effective washing of an oily scalp.
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