Sodium Lauryl Sulfate

Sodium Lauryl Sulfate (SLS) is a surfactant, cleansing agent, and foaming agent. You'll find it in a wide range of products from shampoos to face cleansers.

It:

• lowers surface tension so water can lift away oil, dirt, and product buildup
• produces a rich lather that many people associate with feeling "clean"

The Cosmetic Ingredient Review Panel has assessed it in 1983, 2002, and 2005 and found it to be safe in formulations at low concentrations.

Irritation

SLS is a well-documented skin irritant at higher concentrations or with prolonged exposure. It's actually the gold standard positive control used in dermatological patch testing, meaning doctors use it because they know it will cause a reaction in people.

In one large study of 43,000 patiences tested with 0.25% SLS, about 22% showed some level of reactivity. It increases transepidermal water loss that disrupts your outermost layer of skin.

Face cleansers often pair this ingredient with mild co-surfactants like Cocamidopropyl Betaine to buffer its harshness.

Just so you know, SLS does not trigger true allergic contact dermatitis. This just means it can irritate your skin but doesn't cause your immune system to develop a lasting allergy to it.

Despite internet rumors, SLS is not considered a carcinogen by any major regulatory body.