What do sulfates do to your hair and why are they in shampoo? Everything to know

Wondering to yourself, what do sulfates do to your hair and are they safe? We asked a couple of experts to clear the fog for good

image of woman washing hair in the shower
(Image credit: Getty)

“Sulfates” is a word that gets thrown around a lot in the hair space. So what are sulfates in shampoo and what do sulfates do to hair? 

These days, if you take a quick trip down the drugstore aisles, whether you're in search for your next volume-adding product or trying the curly girl method for beginners, you’ll spot dozens of shampoos labelled as being “sulfate-free”—which may prompt you to wonder if they’re something you should skip.

Whether you prefer using one of the best shampoo bars or a liquid formula, we asked an expert: what do sulfates do to your hair and what are their function in shampoo?

Meet the experts on sulfates

  • Anabel Kingsley (opens in new tab) is a trichologist at Philip Kingsley haircare
  • Michelle Sultan (opens in new tab) is a celebrity hairstylist and Creative Director for curly hair brand Imbue

What do sulfates do to your hair—and why are they in shampoo?

That lather that builds up when you add shampoo bars or liquid shampoo to your wet hair? Chemical foaming agents present in the shampoo are responsible, often in the form of sulfates. Examples of these agents include sodium laureth sulfate and lauryl sulfate, often referred to as SLS.

So, what do sulfates do to your hair? We’re glad you asked. Sulfates come in handy to help your shampoo mix with water, and are responsible for the resulting foamy texture you get when you massage shampoo into your hair, the satisfying bit of double shampooing.

"Sulfates have long been added to all manner of cleansing products because of their ability to emulsify oil and greasy substances, creating a lather that leaves hair and skin feeling clean," trichologist Anabel Kingsley (yep, Philip Kingsley (opens in new tab)'s daughter!), tells My Imperfect Life. 

back view of woman with curly hair pulling single strand

(Image credit: Getty Images)

"They're derived from sulfur and lauryl alcohol," she continues. "This basic reaction can produce hundreds of different sulfates, but 'sodium laureth' SLES and 'sodium lauryl' SLS are those you'll see listed most often."

“The function of sulfates in shampoo is to act as a cleaning agent to strip dirt, oil and build up in the hair," adds Michelle Sultan, celebrity hairstylist and Creative Director for curly hair brand Imbue (opens in new tab) (who make one of the best shampoos for curly hair!). "They were used in shampoo before the correlation was made between dry hair and sulfates, and the way they can dehydrate the hair shaft to cause scalp and hair issues."

So...are sulfates safe?

Frequent use of shampoos with a high concentration of sulfates may have an impact on certain hair and scalp types over time—but they're not "unsafe".

"Sulfates are totally fit for purpose, however some sulfates can irritate sensitive scalps, cause frizziness in thick or curly hair and accelerate colour fade," Anabel explains, so it isn't ideal for curly hair types

While scalps that are already sensitive may benefit from avoiding sulfates, this ingredient should not sensitize non-sensitive skin types. A 2015 study published in the Environmental Health Insights journal (opens in new tab) says that: “There is no scientific evidence to support that SLS has sensitization potential [and] SLS is not included on any lists of known or suspected sensitizers. Therefore, stating that SLS is a sensitizer is inaccurate.”

"It is always important to look at a formulation as a whole versus one particular ingredient," Anabel continues. "If a product is well formulated for a specific concern or hair texture, it should fulfil its intended purpose and be perfectly beneficial."

Elaborating on her curly hair tips, Michelle adds: "Curly or textured hair is prone to being dry or dehydrated due to the fact that it takes longer for natural oils to reach the full length of the hair.

"It’s best to avoid sulfates (and any drying alcohols) that will strip and dehydrate the hair any more than it needs to be." Imbue offers two sulfate-free cleansers, the Coil Awakening Cream Cleanser and their Curl Liberating Cleanser, which is a low-poo shampoo

Should I avoid sulfates in shampoo or not?

Lots of people can use sulfates without any negative repercussions—if you've been double shampooing with a shampoo that contains sulfates your whole life and have never noticed any issues, then as you were.

But as already mentioned, there are groups of people for whom swerving sulfates in shampoo is a good idea. To recap...

  • People with skin conditions or sensitivity. Sulfates aren't really suitable for people with sensitive hair or scalps. If you have skin conditions like eczema or psoriasis, it's worth switching to a sulfate-free formula.
  • People with curly hair. Sulfates are known to increase hair dryness when they strip it of its natural oils and moisture. Curly hair tips always detail that this hair type is already naturally dry (the more bends in your hair, the harder it is for natural oil to migrate down the hair shaft), and so are encouraged to use sulfate-free formulas, aka low poo shampoos, to keep their curl pattern springy.
  • People with colored hair. If you love to color your hair, then sulfates are a big no for you, as they may cause the color to fade more quickly—meaning your fresh color doesn’t last for quite so long and will lead you to search for how to repair damaged hair before long. 
Aleesha Badkar
Deputy Editor at My Imperfect Life

Aleesha is deputy editor and beauty & fashion lead for My Imperfect Life, where she heads up the beauty, fashion and eCommerce pages. Previously she was shopping writer for woman&home and gained an AOP awards nomination after working on their news team. She earned an MA in Magazine Journalism from City, University of London in 2017 and has since worked with a number of brands including, Women's Health, Stylist and Goodto. When she’s not testing new products, Aleesha spends her time soaking up the newest bestsellers and Netflix releases, learning about different wines, attempting new languages and travelling as much as she can.