Sulfates in Shampoo: What the Research Shows
Sulfates are the cleansing agents that make shampoo foam. The research does not show them to be dangerous, but they can irritate some scalps, so the right shampoo depends on your skin and hair rather than on a label trend.
Sulfates are among the most searched ingredients on any shampoo bottle, and also among the most misunderstood. Some people avoid them on principle. Others have never given them a thought. The honest answer sits between the two, and it is more useful than either extreme.
What sulfates are and why shampoo contains them
Sulfates are chemicals used as cleansing agents. The two you will see most often on a shampoo label are sodium lauryl sulfate and sodium laureth sulfate, often shortened to SLS and SLES, as Healthline explains. They belong to a group of ingredients called surfactants, which help water lift oil and dirt away from the hair and scalp so it can be rinsed off. They are also the reason a shampoo lathers. Dermatologist Nicole Rogers, MD, describes sulfates in an American Academy of Dermatology statement as a popular type of detergent that produces a lathering effect.
What the research says about irritation
The most rigorous source here is the Cosmetic Ingredient Review Expert Panel, an independent group that evaluates cosmetic ingredient safety. In its final report on sodium laureth sulfate and related salts, published in the International Journal of Toxicology, the panel found that sodium laureth sulfate was a dermal and ocular irritant but not a sensitizer. It also noted that these ingredients are not regularly seen to be irritating in practice because of the formulations they are used in, and concluded they should be used only when they can be formulated to be nonirritating.
In plain terms, a sulfate on its own can irritate skin and eyes, but a well-made shampoo is designed to keep that in check. Formulation matters as much as the ingredient. Dermatologists also point to contact time. Dr. Zakia Rahman of Stanford told TODAY that irritation tends to occur when these ingredients are left on the surface of the scalp, which is a good reason to rinse thoroughly.
What is not proven
Two claims circulate widely, and neither is supported by the sources we reviewed.
Sulfates cause cancer. Healthline reports that this was once a common perception that further scientific evidence debunked, and dermatologist Brendan Camp told TODAY there is no evidence linking SLS or SLES to cancer.
Sulfate-free shampoo is automatically gentler. The American Academy of Dermatology statement says there is no scientific evidence that the sulfate-free component makes a shampoo gentler, and that claims about preserving color or keratin treatments are not backed by data.
Sulfate-free shampoos can be beneficial for people with a sulfate allergy, and they tend to cost more, but the label alone does not make a product milder.
Who may prefer a sulfate-free formula
Sulfates remove natural oils along with dirt, which is why the same dermatology statement notes they can be harsh for color-treated or chemically treated hair. It also says people with eczema or sensitive skin may not tolerate them, and that there are a few reports linking them to contact dermatitis. Healthline lists redness, rash, swelling, itching and hives as signs of a sulfate sensitivity. TODAY's dermatologists suggest that people with drier hair or sensitive skin may want to consider a sulfate-free option, and note that these shampoos lather less but still cleanse.
If you notice persistent itching, redness or flaking after washing, that is worth raising with a dermatologist rather than solving by changing labels alone.
How to choose and use a shampoo
Read the whole label, not just the sulfate line. A shampoo is a complete formula, and how it feels on your scalp is better evidence than any single ingredient. Wet the hair fully, use a modest amount, massage the scalp gently, and rinse until the water runs clear. If your scalp feels tight or itchy afterward, try a different formula and give it a few washes before judging it.
Each product page lists that formula's ingredients, which is the right place to check what a specific product contains. Two products from our shop that fit a thoughtful wash-day routine are below.
Explore the Royal Treatment Bundle for a complete wash-day routine.
For a finishing step in your routine, see the Crown Care Scalp & Haircare Therapy Oil.
Sources
This article is for educational purposes only and is not medical advice. It is not intended to diagnose, treat, cure or prevent any condition. Talk with a qualified healthcare provider about skin or scalp concerns.
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