Is sulphate-free shampoo really better? Who is it for, and which claims are myths?

What are sulphates and what do they do in shampoo?

When people talk about “sulphates” in shampoo, they usually mean two ingredients: Sodium Lauryl Sulfate (SLS) and Sodium Laureth Sulfate (SLES). These are anionic surfactants: one end of the molecule clings to water and the other to oil, so they remove sebum, dirt and styling product residue from the scalp along with the water.

Because they are cheap, effective and produce plenty of lather, they have been the main cleanser in shampoos for decades. The problem is that their cleansing power can be too much for some people: they can strip more of the scalp's natural oils than expected, leading to dryness, tightness or itching. Thanks to the ethoxylation process, SLES is milder than SLS; this is why our app also rates it in a lower risk range.

There is an important detail here: shampoo is a rinse-off product. The cleanser stays on the scalp for only a minute or two and is then washed away with water. So SLS in shampoo does not have the same effect as SLS in a cream that stays on the skin for hours. The risk of irritation is determined by a combination of concentration, contact time and the person's skin.

Who might benefit from sulphate-free shampoo?

• People with a dry, sensitive or eczema-prone scalp: Milder cleansers put less strain on the skin barrier; itching and flaking may lessen.
• People with curly and wavy hair: Because these hair types are naturally drier, gentle formulas that preserve moisture usually work better.
• People with coloured hair: With frequent washing, strong cleansers can help colour fade faster; this is why sulphate-free products are often recommended for coloured hair.
• People who have had a keratin or similar smoothing treatment: Stylists and product makers usually recommend sulphate-free shampoo to make the treatment last.
• People who wash their hair often: If you wash your hair every day, a gentler cleanser may dry your scalp less.

If your scalp is oily, you use a lot of styling products or you swim in pools often, the stronger cleansing of a sulphate shampoo may suit you better. Some people also prefer to alternate between the two types of product.

Common myths and the facts

• “Sulphates cause cancer.” This claim has no scientific basis. SLS and SLES are not classified as carcinogens by IARC or the European Union. The confusion stems from 1,4-dioxane residue, which can form in trace amounts during the production of SLES; this residue is minimised by purification.
• “Sulphates make your hair fall out.” There is no evidence that sulphates affect the hair roots and cause hair loss. Hair loss can have many hormonal, nutritional or genetic causes; in that case you should see a dermatologist.
• “If there's no lather, it isn't cleaning.” The amount of lather is not a measure of cleansing power. Sulphate-free shampoos may lather less, but they still clean the hair.
• “Sulphate-free products contain no chemicals.” Sulphate-free shampoos also contain surfactants, preservatives, thickeners and often fragrance. What changes is the type of cleanser.
• “Sulphate-free shampoo leaves the scalp dirty.” On an oily scalp it may sometimes not feel strong enough; but this does not mean the product is bad, only that it does not suit that hair type.

Which cleansers do sulphate-free shampoos contain?

“Sulphate-free” shampoos use different surfactants instead of sulphates. The main ones you will often see on labels are:

• Cocamidopropyl betaine: an amphoteric, mild secondary cleanser. Although rare, contact allergy linked to impurities left over from manufacturing has been reported in some people.
• Coco-glucoside, Decyl Glucoside, Lauryl Glucoside: very mild cleansers derived from sugar and plant oil.
• Sodium Cocoyl Isethionate, Sodium Lauroyl Sarcosinate, Sodium Cocoyl Glutamate: gentler anionic cleansers.
• Sodium C14-16 Olefin Sulfonate: technically a “sulphonate”, not a “sulphate”, and it cleanses quite strongly. Even if the product is sold as sulphate-free, it can be nearly as drying as SLES.

So the word “sulphate-free” alone does not guarantee that a product is mild. What you really need to check is which main cleanser is in second or third place on the list.

What to check on the label

• Find the main cleanser: The first one or two ingredients after water (Aqua) are usually the main cleanser.
• Watch out for fragrance: Sometimes the real problem for a sensitive scalp is not sulphate but fragrance. A sulphate-free but heavily fragranced product can cause the same discomfort.
• Look at the conditioning ingredients: Ingredients such as glycerin, panthenol or dimethicone help hair feel softer.
• Check the preservative: If you have previously been diagnosed with an allergy to a preservative, look for that substance in sulphate-free products too.

For general shampoo label reading techniques, see also our how to read a shampoo label guide.

The transition period and tips for use

When you switch from a sulphate shampoo to a sulphate-free one, your hair may feel different for the first few washes: less lather and a slightly heavier or softer texture. This is normal. With products that lather less, spreading the shampoo over the scalp first, massaging with your fingertips and then rinsing thoroughly improves cleansing.

If you use a lot of styling products, dry shampoo or heavy oils, using a clarifying shampoo once a week or once every two weeks can remove build-up. If you have persistent itching, redness or sores on your scalp, don't just change products; see a dermatologist.