Sulfates in shampoo: are SLS and SLES bad for you?
Are sulfates bad? What sodium lauryl sulfate and SLES do in shampoo, SLES vs SLS, who benefits from sulfate-free shampoo and milder cleansers to look for.
By the Green Point editorial teamUpdated 6 min readKey takeaways
- Sulfates such as sodium lauryl sulfate (SLS) and sodium laureth sulfate (SLES) are cleansing agents that remove oil and make shampoo lather.
- They aren't dangerous in rinse-off products, but they can strip oil and irritate sensitive skin and scalps.
- SLES is generally milder than SLS; how a shampoo is formulated matters as much as which sulfate it contains.
- Sulfate-free shampoos can help with dry, curly, color-treated or easily irritated hair and scalps.
- Milder cleansers include glucosides (such as decyl glucoside) and amphoteric surfactants such as cocamidopropyl betaine.
On this page
Sulfates in shampoo, mainly sodium lauryl sulfate (SLS) and sodium laureth sulfate (SLES), are strong cleansing agents. They aren't harmful in a rinse-off shampoo, and there's no good evidence they cause cancer. But they can strip natural oils and irritate sensitive skin, so a sulfate-free shampoo can help if your hair is dry, curly or color-treated or your scalp is easily irritated.
What do sulfates do in shampoo?
Sulfates are surfactants: molecules with one end that attracts water and one that attracts oil. They surround oil, sweat, dead skin and styling product residue so water can rinse it away. They also make rich lather, which many people associate with feeling clean.
They belong to a group called anionic surfactants, which are very effective cleansers. A dermatology review of shampoos describes lauryl sulfates as excellent cleansers often used for oily hair, but notes that hair cleaned too thoroughly can feel rough, dull, frizzy and prone to tangling.
| Name on the label | Short name | What to know |
|---|---|---|
| Sodium lauryl sulfate | SLS | Strong cleanser; the most likely to irritate |
| Sodium laureth sulfate | SLES | Modified form of SLS; generally milder |
| Ammonium lauryl sulfate | ALS | Similar strong cleanser to SLS |
| Ammonium laureth sulfate | ALES | Similar to SLES |
| Sodium C14-16 olefin sulfonate | – | Not a sulfate, but also a strong cleanser found in some "sulfate-free" shampoos |
SLES vs SLS: what's the difference?
SLES is made from SLS through a process called ethoxylation, which makes the molecule larger and less able to disturb the skin. In practice, SLES is generally considered milder, which is why it's more common in shampoos and body washes.
Ethoxylation can leave traces of a byproduct called 1,4-dioxane. It isn't an ingredient, and the FDA says levels in cosmetics have declined significantly over time as manufacturers changed their processes. International reviews cited by the FDA found trace levels within acceptable safety margins.
Are sulfates bad for you?
For most people, no. Sulfates in rinse-off products are on your skin for a minute or two before being washed away. The issues are about comfort and irritation, not long-term health:
- Irritation: SLS is a well-known skin irritant. It's used in research as a reference irritant because it reliably disrupts the skin barrier in controlled skin tests, causing water loss and redness with prolonged exposure. Short contact in a shampoo is very different, but people with sensitive skin may notice stinging or itching.
- Dryness: strong cleansing removes the natural oils that keep hair soft, which matters more for dry, curly or coily hair.
- Eczema and sensitive skin: people with eczema or a sensitive scalp may find sulfate products more irritating. Shampoo also runs down your face, neck and back.
The claim that sulfates cause cancer has circulated for years, but there's no good evidence for it. Sulfate allergy is also uncommon: reactions are usually irritation rather than a true allergy.
Who benefits from sulfate-free shampoo?
Sulfate-free shampoo isn't automatically "healthier", but it can make a real difference if you have:
- Dry, curly or coily hair that loses moisture easily
- A sensitive or itchy scalp, eczema or skin that reacts to many products (see our sensitive skin guide)
- Color-treated hair: gentler cleansers are commonly recommended to help color last, and shampoo makers tend to use milder detergents for dyed or permed hair
- Chemically treated hair, such as after a perm, relaxer or smoothing treatment, where the stylist recommends it
If your hair is oily, you use a lot of styling products or you swim often, a sulfate shampoo may suit you better, or you can alternate it with a gentler one.
Milder alternatives to look for
Sulfate-free shampoos use gentler surfactants, often several together. On the label, look for:
- Glucosides: decyl glucoside, coco-glucoside, lauryl glucoside. These non-ionic surfactants, made from sugars and fatty alcohols, are among the mildest cleansers.
- Amphoteric surfactants: cocamidopropyl betaine is common in baby shampoos because it causes less eye stinging. It has occasionally been linked to allergic reactions, which are often blamed on impurities left over from manufacturing.
- Isethionates and taurates: sodium cocoyl isethionate and sodium methyl cocoyl taurate are gentle and still lather reasonably well.
- Sarcosinates and sulfosuccinates: such as sodium lauroyl sarcosinate and disodium laureth sulfosuccinate.
Expect less foam. Less lather doesn't mean less clean; it's mostly a sign of a milder surfactant. Concentrate shampoo on your scalp, where the oil is, and let it rinse through the lengths. If you're also reconsidering silicones, see silicones in skincare and hair care.
How Green Point rates sulfates
Green Point marks sodium lauryl sulfate and sodium laureth sulfate with a "Sulfate" classification, and they lower a shampoo's score. That reflects their irritation potential, not a health hazard in normal use. Tap the ingredient in the app to see what it does and why it's flagged. To find sulfates and their alternatives on any label yourself, read how to read a cosmetic ingredient list.
Frequently asked questions
Does sulfate-free shampoo clean as well?
For most people, yes. Sulfate-free shampoos clean well enough for everyday use, especially if you massage them into the scalp and rinse thoroughly. They may struggle more with heavy oil, waxy styling products or swimming pool residue. In that case, an occasional clarifying shampoo (which often contains sulfates) can help.
Do sulfates cause hair loss?
There's no good evidence that sulfates cause hair loss. They can make hair dry and brittle, especially if it's already damaged, and brittle hair can break, which may look like thinning. True hair loss has many causes, including genetics, hormones, illness and stress. See a dermatologist if you're losing more hair than usual.
Is sodium laureth sulfate safe in body wash and toothpaste?
Yes, at the levels used it's considered safe in rinse-off products like body wash. Some people with sensitive or eczema-prone skin find it drying and prefer milder cleansers. Some toothpastes contain SLS rather than SLES; if you get frequent mouth irritation, an SLS-free toothpaste is an easy change to try. Ask your dentist about recurring mouth ulcers.
Why does my hair feel greasy after switching to sulfate-free shampoo?
Milder cleansers remove less oil and product buildup, so your hair may feel heavier at first, especially if you use silicones or rich styling products. Try washing twice, focusing on the scalp, or use a clarifying shampoo occasionally. If your hair stays greasy after a few weeks, a sulfate-free formula may simply not suit your hair type.
Sources
- Shampoo and Conditioners: What a Dermatologist Should Know?Indian Journal of Dermatology (via PMC)
- 1,4-Dioxane in Cosmetics: A Manufacturing ByproductU.S. Food and Drug Administration
- Specific barrier response profiles after experimentally induced skin irritation in vivoContact Dermatitis (via PMC)
This guide is for general information and is not medical advice. If you have a skin, allergy or health concern, talk to a doctor, dermatologist or dietitian. Green Point scores and Skin Scan results are informational and are not a diagnosis.
