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Ingredient: Laureth-4

Fast Facts

Type of Ingredient: Foaming agent

Main Uses and Benefits: Creates a lather and aids in deep cleaning. Also emulsifies formulas.

Find It In: Moisturizers to counteract the dryness from sodium lauryl sulfate

How Often Can You Use It: Can be used every day as long as you don’t have an allergy or sensitivity to it. Only apply it to areas that harbor bacteria to limit the amount of time on your skin. Don’t use it with physical and chemical exfoliants, as doing so may further irritate the skin. Due to how it is made, laureth-4 may contain traces of 1,4, dioxane, a possible carcinogen.

What Is Laureth-4 in Skincare?

Laureth-4 is derived from lauryl alcohol and is a clear, colorless liquid. Lauryl alcohol is obtained from lauric acid, a saturated fatty acid with a 12-carbon atom chain that can be found in palm kernel oil or coconut oil.

The number associated with the laureth (i.e. laureth-4) indicates the average number of repeating ethylene oxide units in the molecule. The higher the value, the greater the viscosity, until it becomes a waxy, white solid.

Laureth-4 is created through ethoxylation, a process that produces 1,4-dioxane as a byproduct. 1,4-dioxane is a known animal carcinogen.

The Benefits of Laureth-4

1. Surfactant

Laureth-4 works by lowering the surface tension between two substances, such as two liquids or a liquid and a solid. A surfactant molecule contains one hydrophilic end (attracted to water) and one lipophilic end (attracted to oil). This allows surfactants to attract and suspend oils, dirt, and other impurities that have accumulated on the skin and wash them away.

Surfactants can be found in many different cleansers and body washes.

2. Emulsifier

Emulsifiers improve the consistency of a product, which enables an even distribution of topical skincare benefits. They are especially necessary when a formula contains both water and oil components. Mixing water and oil creates a dispersion of oil droplets in water (and vice versa). However, these two phases can separate if the product is left to settle. To address this problem, an emulsifier, like laureth-4, can be added to the formula to help the droplets remain dispersed.

Sodium Lauryl Sulfate vs. Sodium Laureth Sulfate: What’s the Difference?

Two sulfates that commonly occur in beauty products either separately or together are sodium lauryl sulfate (SLS), also known as sodium dodecyl sulfate (SDS), and sodium laureth sulfate (SLES). Laureth-4 is in SLES, just without the sodium.

Because of the slight variation in spelling, these two ingredients are easy to confuse, but there is a notable difference between the two. They function similarly in the sense that both ingredients create that foamy feel in products, but sodium lauryl sulfate (SLS) binds to proteins on the skin's surface more than sodium laureth sulfate (SLES). What this means is that sodium lauryl sulfate (SLS has the potential to be more irritating due to the higher rate of contact.

Laureth-4 Safety: Is Laureth-4 Bad?

The Cosmetic Ingredient Review (CIR) Expert Panel evaluated the scientific data and concluded that the laureth-4 was safe to use in cosmetic products only when formulated to be non-irritating.

Is Laureth-4 a Carcinogen?

Even though laureth-4 is considered a safe cosmetic ingredient by the CIR Expert Panel, there are concerns about the presence of ethylene oxide in this component. As mentioned above, laureth-4 is created through ethoxylation, a process that produces 1,4-dioxane as a byproduct. 1,4-dioxane is a known animal carcinogen that penetrates deeply into the skin. According to the National Toxicology Program, “1,4-dioxane is reasonably anticipated to be a human carcinogen.” It has also been linked with skin allergies.

The Organic Consumers Organization released a fact sheet on 1,4-dioxane based on information from the Campaign for Safe Cosmetics. The fact sheet outlines facts versus myths regarding 1,4-dioxane in personal care products. One concerning fact is that the levels of 1,4-dioxane found in many personal care products are 1,000 times higher than those found to cause cancer in animal studies. They add that according to the FDA, “Skin absorption studies demonstrated that dioxane readily penetrates animal and human skin from various types of vehicles.” Therefore, perhaps use caution to avoid products with SLES mainly due to concerns of contamination of 1,4, dioxane.

Can You Be Allergic to Sodium Lauryl Sulfate?

“Most people can use products containing sodium lauryl sulfate (SLS) without worrying about skin or scalp irritation,” says Dr. Stefanie Morris, Dermatologist & Medical Director at European Dermatology London. “This is because it’s a rinse-off product — the contact time is short and, after rinse-off, there is extremely little SLS (if any), which stays on the skin/scalp.”

NYC-based dermatologists Rachel Nazarian, MD, of Schweiger Dermatology Group says although sodium lauryl sulfate (SLS) is not a bad ingredient for most people, it can be an irritant. "If you're going to get it in your eyes or if you’re not going to wash it off your skin and you’re going to leave some of the residues on your skin, it can be irritating," Nazarian says.

As far as allergies go, Nazarian says when a patient comes in with a potential contact allergy, sodium lauryl sulfate is one of the ingredients that they will test for, but it's more of an irritant than it is an allergy. "Anything can be an irritant if it’s used the wrong way or if it’s on the skin too long," she explains. "It’s more likely to be an irritant, meaning we just need to teach people how to use it and how often to use it."

Other potential side effects of SLS include hair loss, liver failure, severe dermal sensitization, reproductive and development toxicity, neurotoxicity, and endocrine disruption.