Sodium Lauryl Sulfate (SLS): The Common Ingredient Hiding in Plain Sight

We use personal care and cleaning products like shampoo and laundry detergent every day without a second thought. We lather, rinse, scrub, and wash. But hiding in many of these everyday items is a chemical that’s raising increasing concern among scientists, health professionals, and conscious consumers: Sodium Lauryl Sulfate, or SLS.

Let’s dive into what SLS is, where it comes from, how it came to be so widely used, and why you may want to think twice before using products that contain it.

What is Sodium Lauryl Sulfate (SLS)?

Sodium Lauryl Sulfate is a surfactant, a substance that lowers the surface tension between ingredients. It’s what makes shampoo foam, toothpaste lather, and soap bubble. Chemically, it is a salt derived from lauryl alcohol, which itself can come from either petroleum sources or natural fats like coconut or palm oil.

Its primary role is to break down grease and oils so that dirt can be rinsed away with water. That sounds useful—and it is. But like many chemicals developed in the name of convenience, SLS has a complicated story.

A Short History of a Long Legacy

Sodium Lauryl Sulfate was first synthesized in the early 1930s. At the time, the modern personal care industry was just beginning to take shape. Manufacturers were searching for ingredients that could create a lot of lather (which consumers associated with cleanliness) and were inexpensive to produce at scale.

SLS checked all the boxes. It foamed. It cleaned. It was cheap. And by the mid-20th century, it had found its way into everything from floor cleaners to facial washes. In fact, many of the formulas developed during World War II for degreasing machinery were later adapted into commercial household and personal care products.

SLS’s popularity exploded in the 1950s and '60s as the era of convenience took hold. Companies marketed heavily around the idea of a spotless, sanitized home—and lather, bubbles, and foam became visual stand-ins for “clean.”

But over time, some started to ask: at what cost?

The Hidden Consequences

Skin & Eye Irritation

One of the most commonly reported effects of SLS is skin irritation. It strips away natural oils from the skin, leaving it vulnerable to dryness, redness, and sensitivity. This is especially true for those with eczema or sensitive skin. A 1983 study in the Journal of the American College of Toxicology found that even small concentrations of SLS could cause “severe epidermal changes” after short-term exposure (1).

Oral Discomfort

When used in toothpaste, SLS has been linked to an increase in canker sores and irritation of the gums and mouth lining. Dentists often recommend avoiding it for patients prone to oral sensitivity.

Eye Development in Children

One concerning discovery from animal studies was that SLS could potentially impact eye development in young mammals. Though these findings haven't been conclusively replicated in humans, they raised enough eyebrows to warrant caution, particularly in baby products (2).

Enhanced Skin Absorption

Perhaps more troubling is the fact that SLS is known to increase the skin's permeability. That means it can allow other chemicals—some of which may be even more harmful—to penetrate deeper into the body. This kind of co-exposure effect is one reason many toxicologists express concern, even if SLS itself is not labeled as a carcinogen (3).

Environmental Impact

SLS is often touted as “biodegradable,” and while that’s technically true, the rate of breakdown and toxicity to aquatic life are still significant issues. Wastewater treatment plants don’t always fully remove it, and residues that reach rivers and oceans can harm fish, invertebrates, and plant life (4).

Why Is It Still So Common?

You might wonder: if we’ve known about these problems for decades, why is SLS still so widely used?

The answer is multi-layered. First, SLS is extremely cheap to produce. For multinational corporations manufacturing products by the millions, cost per unit matters—a lot. Second, consumers have been conditioned to associate lather with effectiveness. In one study, participants rated foaming cleansers as more “clean-feeling” than non-foaming ones, even when their actual cleaning power was equal.

Third, regulations in many countries—including the U.S.—do not require manufacturers to eliminate ingredients unless they’re proven to be acutely toxic. SLS, while irritating, doesn't cause immediate harm in most people at typical concentrations. This gray area allows it to remain in use.

A More Personal Lens

For me, learning about SLS didn’t start with a Google search or a science journal. It started with my wife’s rash.

Years ago, Katrina began breaking out in painful, persistent patches around her mouth and jawline. Doctors diagnosed her with perioral dermatitis—a frustrating and often misdiagnosed skin condition. We tried medications, prescriptions, elimination diets. Nothing worked.

It wasn’t until we stumbled across some research about SLS and skin sensitivity that a lightbulb went off. We started reading ingredient labels and realized SLS was everywhere: in her face wash, her toothpaste, even the so-called “sensitive skin” shampoo she’d trusted for years. We switched to SLS-free alternatives—and the change was immediate. Her skin healed but something else happened too, something we were not expecting. Katrina’s dandruff . disappeared too, for years Katrina has dealt with dandruff and constantly needing to use products like Head and Shoulders.

Not long after, we realized our kids were dealing with similar sensitivities. Eczema flare-ups, red blotchy skin after bath time, unexplained rashes, and dandruff. Once we removed SLS from our household, things started to calm down. What we thought were random allergic reactions turned out to be avoidable chemical exposures.

I grew up on Navajo land in the high desert of Arizona—off-grid, no electricity, hauling water and firewood. I didn't grow up with bleach wipes or synthetic soaps. But I did grow up next to uranium and coal mines. From a young age, I saw how toxic exposure could devastate communities, how industries could poison water, and how easy it was for corporations to write off human health in pursuit of profit.

That perspective stayed with me. Years later, standing in a modern home with my children suffering from chemical-induced skin conditions, it felt like a different version of the same story. We’d traded industrial pollution for something more insidious—chemical saturation in everyday life.

What You Can Do

This isn’t a call for panic—it’s a call for awareness. If you’re concerned about SLS, here are a few simple steps you can take:

• Read labels carefully. Learn to recognize SLS, SLES, ALS, and related sulfates.

• Seek alternatives. Look for products labeled as “sulfate-free.” Many now use coconut-derived surfactants that are gentler on skin.

• Test for sensitivity. If switching to an SLS-free product reduces your irritation or improves your skin, you may have found a better fit.

• Be skeptical of greenwashing. Just because something says “natural” doesn’t mean it’s free from harsh ingredients. Always check the ingredient list.

Final Thoughts

Sodium Lauryl Sulfate may not be the villain in every bottle, but it’s far from innocent. Its long legacy in our personal and cleaning products deserves closer scrutiny—not only for the potential harm it causes, but for what it represents in a culture that often prizes convenience over care.

Understanding ingredients like SLS is about more than chemistry—it’s about choice. It’s about reclaiming control over what we allow into our homes and onto our bodies. And it’s about building a future where clean really does mean safe.

Sources:

[1] Journal of the American College of Toxicology, Vol. 2, No. 7, 1983.
[2] Green, C., & Nissen, L. M. "Sodium lauryl sulfate and its effects on the skin barrier function," Cosmetic Dermatology, 2012.
[3] Api, A. M., Basketter, D. A., et al. "Dermal Absorption and the Relevance of Surfactant-Induced Skin Irritation." Toxicology Letters, 2008.
[4] Ying, G.-G. "Fate, behavior and effects of surfactants and their degradation products in the environment." Environment International, 2006.
[5] U.S. Environmental Protection Agency. Technical Fact Sheet: 1,4-Dioxane. https://www.epa.gov/ground-water-and-drinking-water/technical-fact-sheet-14-dioxane