Overview: Sodium lauryl sulfate (SLS) ranks among the most extensively studied ingredients in dermatology, precisely because researchers rely on it as a controlled irritant to study how the skin barrier responds to damage and recovers. This article walks through what that research actually demonstrates: how SLS increases water loss through skin, what happens when exposure repeats daily, and how glucoside-based alternatives perform by comparison. It closes with why washing frequency changes the stakes of that choice. Skip to any section, or read through for the complete picture.
Why scientists chose SLS as a research tool in the first place
Dermatology researchers have used SLS for decades as a standardised irritant, applying it under controlled laboratory conditions specifically to damage the skin barrier and then measure how it recovers. That research relationship exists because SLS produces reliable, reproducible irritation, which makes it useful for scientific study. It also means the resulting body of research offers unusually detailed insight into what regular sulphate exposure does to skin, insight that applies directly to anyone showering daily after training.
What the research shows about barrier disruption
SLS functions as the surfactant responsible for the thick foaming lather found in many shampoos, body washes, and dish detergents. Manufacturers favour it because it degreases effectively and costs little to produce. The trade-off appears in a measurement called transepidermal water loss, or TEWL, which quantifies how much water escapes through skin rather than remaining locked within it. Multiple clinical studies confirm that SLS increases TEWL in a dose-dependent relationship: higher concentrations produce greater water loss, and the relationship holds consistently across study populations.
One study tracked ceramide levels, the lipid molecules that structurally bind the skin barrier together, across 14 volunteers following SLS exposure. Researchers found that ceramide depletion correlated directly with the degree of irritation each participant experienced. A separate study examining repeated exposure produced a finding with direct relevance for daily showering: skin that had already reacted to SLS once showed an augmented, more severe response on second exposure, even after the skin had visibly returned to normal in the interim. The skin barrier, in other words, does not necessarily achieve a complete reset overnight between one shower and the next.
Water hardness compounds the effect further. Research measuring surfactant deposition found that washing with hard water significantly increases the amount of SLS residue left on skin after rinsing, which in turn increases both water loss and irritation. This effect proves most pronounced in skin that already carries a compromised barrier, including in populations with an underlying predisposition such as atopic dermatitis.
Why cumulative exposure matters more for active bodies
None of this research applies equally to everyone. A person showering once or twice daily, most days of the week, accumulates substantially more sulphate exposure over a month than someone washing only occasionally. Add the additional variables that come with regular training, including sweat, friction from equipment and clothing, and, in the Australian context, frequent sun and chlorine exposure from pool or ocean sessions, and the skin barrier already carries a heavier load before a harsh surfactant enters the equation. The research on repeated SLS exposure suggests this load compounds rather than resets between sessions.
Why sulphate-free doesn't mean a weaker clean
A common assumption holds that removing sulphates from a formulation sacrifices cleaning performance. The comparative research does not support that assumption. Lauryl glucoside, a plant-derived, non-ionic surfactant manufactured from corn starch and coconut-derived fatty acids, has been tested directly against SLS in clinical patch-testing studies alongside sodium laureth sulfate (SLES), consistently showing a substantially lower irritation profile. Coco glucoside, a closely related surfactant, demonstrates a similar profile in independent testing.
Large-scale patch testing offers additional context on sensitivity. Glucoside surfactants as an ingredient category produce a genuine allergic reaction in approximately 0.25 percent of tested individuals, a rate low enough to place them among the least sensitising surfactant classes available for cosmetic formulation. This combination, comparable cleansing performance alongside substantially lower irritation potential, explains why glucoside-based surfactants have become the standard choice in formulations designed specifically for frequently washed, activity-exposed skin.
What this means in practice
Anyone washing daily faces a materially different set of stakes around surfactant choice than someone washing twice a week. A sulphate-based formula asks more of a skin barrier that, for anyone training regularly, is already managing sweat, friction, and environmental exposure on top of daily cleansing. The research indicates that a glucoside-based, sulphate-free formulation reduces that cumulative demand without requiring a trade-off in cleaning performance. Understanding that distinction is worth the extra thirty seconds spent reading a label before it goes in the shopping trolley.
References
- Agner, T. & Serup, J. "Sodium lauryl sulphate for irritant patch testing: A dose-response study using bioengineering methods for determination of skin irritation." Journal of Investigative Dermatology, 1990.
- "Sodium lauryl sulfate (SLS) induced irritant contact dermatitis: a correlation study between ceramides and in vivo parameters of irritation." PubMed ID: 8917825.
- Freeman, S. & Maibach, H.I. "Study of irritant contact dermatitis produced by repeat patch testing with sodium lauryl sulphate and assessed by visual methods, transepidermal water loss and laser Doppler velocimetry." Journal of the American Academy of Dermatology.
- Danby, S.G. et al. "The Effect of Water Hardness on Surfactant Deposition after Washing and Subsequent Skin Irritation in Atopic Dermatitis Patients and Healthy Control Subjects." Journal of Investigative Dermatology, 2018.
- "Profile of irritant patch testing with detergents: sodium lauryl sulfate, sodium laureth sulfate and alkyl polyglucoside." Comparative clinical patch-testing study.
Dermogains products are cosmetic skincare formulations only. Nothing in this article, including the studies referenced above, constitutes a claim that any Dermogains product treats, cures, or prevents any medical or skin condition, including atopic dermatitis or any other condition named in the cited research.