Sodium Lauryl Sulfate (SLS) is one of the most widely used surfactants in the personal care industry. Found in everything from shampoos to toothpaste, body washes, and facial cleansers, it is a powerful cleansing and foaming agent that has sparked ongoing debate about its effects on human health and the skin. While effective at removing dirt and oil, SLS is also known for its potential to cause skin irritation and dryness, making it a controversial ingredient in modern skincare.
This article will explore what Sodium Lauryl Sulfate is, how it is manufactured, its role in skincare formulations, its impact on consumers, and why many brands—particularly in the clean beauty movement—are moving away from its use.
Sodium Lauryl Sulfate (SLS) is a synthetic detergent and surfactant, meaning it lowers the surface tension of water, allowing it to mix with oils and dirt for easy rinsing. It is part of a broader class of chemicals known as sulfates, which also include Sodium Laureth Sulfate (SLES) and Ammonium Lauryl Sulfate (ALS). SLS is an anionic surfactant, which means it carries a negative charge, contributing to its ability to lift oils and grime from surfaces, including the skin and hair.
Its molecular structure consists of a lauryl (12-carbon) hydrophobic tail and a hydrophilic sulfate head, which makes it an effective emulsifier and cleanser.
SLS is derived from lauryl alcohol, which can be sourced from both petroleum and natural plant oils (such as coconut or palm oil). The production process involves several steps:
Derivation of Lauryl Alcohol:
Sulfonation:
Neutralization:
The production process varies slightly depending on whether SLS is derived from petrochemical or plant-based sources, but the end product is chemically identical.
SLS serves multiple functions in personal care products, making it a staple in mass-market formulations.
SLS is an effective detergent, breaking down oils, sebum, and dirt so they can be easily rinsed away with water. This makes it useful in facial cleansers, body washes, and shampoos.
Consumers associate thick, rich lather with effective cleansing. SLS is a strong foaming agent, creating a voluminous lather that enhances the sensory experience of using shampoos, body washes, and toothpaste.
In formulations containing oils and water, SLS helps blend the two, preventing separation and ensuring a uniform product. This property is critical in lotions, liquid soaps, and some makeup removers.
Compared to milder surfactants, SLS is inexpensive and widely produced, making it attractive for budget-friendly and mass-market skincare formulations.
While SLS is effective at cleansing, it also has several notable drawbacks that raise concerns among dermatologists, skincare professionals, and consumers.
SLS is classified as an irritant, particularly in high concentrations. Studies have shown that it can strip the skin of its natural lipids, leading to dryness, tightness, and increased transepidermal water loss (TEWL).
Because SLS is a powerful degreaser, it can remove not only dirt and oils but also the natural moisture that the skin and scalp need to remain healthy. This effect is particularly pronounced in individuals with dry or eczema-prone skin.
Regular use of SLS-containing products may lead to increased sensitivity over time, making the skin more reactive to external irritants such as pollution, harsh weather, or even other skincare ingredients.
In toothpaste and facial cleansers, SLS can cause stinging and irritation when it comes into contact with the eyes or mucous membranes. This is a primary reason why some brands have switched to gentler alternatives in oral care products.
There has been speculation and misinformation regarding SLS being linked to cancer, but scientific research has not confirmed any carcinogenic properties. However, because SLS can be contaminated with 1,4-dioxane (a byproduct of ethoxylation in SLES), some concerns exist regarding its purity and potential health effects.
The shift toward clean beauty and sensitive skin formulations has led to a decline in the use of SLS in high-end skincare and haircare products. Many brands now use milder, sulfate-free surfactants such as:
Brands that emphasize gentle cleansing, hydration, and barrier repair often avoid SLS to cater to consumers with sensitive skin or those looking for more skin-friendly alternatives.
Sodium Lauryl Sulfate is an undeniably effective surfactant that plays a significant role in skincare and personal care products. However, its drawbacks—especially its potential to cause irritation, dryness, and barrier disruption—have made it a controversial ingredient. While not inherently toxic or carcinogenic, its harsh cleansing properties make it less suitable for individuals with sensitive or dry skin.
As consumer demand for gentler, sulfate-free formulations grows, many brands are reformulating their products to exclude SLS in favor of milder alternatives. However, it remains widely used in lower-cost and high-foaming cleansers, shampoos, and oral care products.
For those with sensitive or compromised skin, avoiding SLS may be a wise choice in maintaining optimal skin health. However, for those with resilient, oil-prone skin, occasional use of SLS-containing products may not pose a significant issue—provided they are followed by adequate hydration and barrier-repairing skincare.
Ultimately, whether to use or avoid Sodium Lauryl Sulfate comes down to personal preference, skin type, and tolerance levels. However, as skincare science continues to evolve, it is clear that gentler alternatives are becoming the new standard in modern formulations.