Sulfates serve as surfactants in personal care products such as skin cleanser and shampoo. The word surfactant is a shortening of surface-active agent. Surfactants reduce surface tension in liquids, making them useful in removing oil and debris from skin and hair. Sodium lauryl sulfate (SLS) and sodium laureth sulfate (SLES) are two of the most common sulfates found in skin and haircare.
The GOOD: It is hard to match their foaming performance, and they are inexpensive.
The BAD: There is strong evidence that they cause skin irritation. Leave-on formulas are especially risky. A high concentration of sulfates in a rinse-off formula can also pose a problem. As an example, check out the evidence on SLES irritation through the Environmental Working Group or Cosmetic Ingredient Review.
Bottom-line: People with sensitive skin conditions (such as rosacea) or a compromised skin barrier (as in eczema or psoriasis) should avoid sulfates in their personal care products. Shopping “sulfate-free” labels is helpful, but doesn’t guarantee that the formula is non-irritating (nor do words on a label like hypoallergenic, gentle, or sensitive — more on that in another post). See if the brand shares the product’s patch testing result (see the MeridaSKIN Foaming Facial Cleanser as an example).