What Is SLS (Sodium Lauryl Sulfate)?

This post was written with Consensus AI Academic Search Engine – please read our Disclaimer at the end of this article. Sodium Lauryl Sulfate (SLS) is a widely used surfactant found in various personal care products, including toothpastes, shampoos, and soaps. It is known for its ability to create a lathering effect, which enhances the cleaning efficiency of these products. However, SLS has also been associated with several adverse effects, particularly concerning skin and mucosal irritation.

Chemical Properties and Uses

SLS is a detergent and surfactant that decreases the surface tension of water, allowing it to more effectively interact with oils and dirt. This property makes it a common ingredient in cleaning and personal care products. Most commercially available dentifrices contain between 0.5% and 2.0% SLS7.

Effects on Skin and Mucosa

Skin Irritation

SLS is a known irritant and is often used in dermatological studies to induce irritation for testing the efficacy of topical formulations. For instance, SLS-induced contact dermatitis is a standard model for evaluating the effects of different topical treatments1. It has been shown to cause significant local inflammation and primary hyperalgesia to tactile and thermal stimulation, with effects lasting up to 2-3 days3.

Oral Mucosa

In the oral cavity, SLS can cause desquamation of the oral epithelium. A study involving dental hygiene students demonstrated that toothpastes containing 1.5% SLS provoked desquamation in 60% of the subjects2. Additionally, SLS has been implicated in the exacerbation of recurrent aphthous stomatitis (RAS), where SLS-free dentifrices were found to reduce the duration and pain of ulcers compared to SLS-containing dentifrices4 9.

Clinical Studies and Findings

Gingivitis and Plaque

The effectiveness of SLS-containing dentifrices in managing gingivitis and plaque has been compared to SLS-free alternatives. A study involving young adults found no significant difference in gingival bleeding and plaque scores between the two types of dentifrices. However, participants preferred the foaming effect of SLS-containing dentifrices5.

Wound Healing

SLS has been shown to inhibit wound healing in vitro. In a study using primary human gingival fibroblasts, SLS demonstrated a dose- and time-dependent inhibition of wound fill, suggesting that SLS-containing products might delay oral wound healing7.

Reproducibility in Patch Tests

SLS is also used in patch tests to evaluate skin irritability. A study found that a 1% SLS solution provided sufficiently reproducible results for irritant patch tests, making it a reliable standard for such assessments6.

Alternative Uses

Veterinary Applications

SLS has been explored as an alternative to mulesing in lambs. Intradermal injection of SLS induced mild swelling and scab formation, with physiological and behavioral responses that were intermediate between mulesed lambs and controls8.

Bad Breath

SLS-containing dentifrices have been shown to reduce the formation of volatile sulfur compounds (VSCs), which are responsible for bad breath. A study found that SLS-containing dentifrices were more effective in reducing organoleptic scores and VSC levels compared to SLS-free alternatives10.

Conclusion

Sodium Lauryl Sulfate is a versatile surfactant widely used in personal care products for its effective cleaning properties. However, its potential to cause skin and mucosal irritation, delay wound healing, and exacerbate conditions like recurrent aphthous stomatitis necessitates careful consideration of its use. While SLS-containing products are effective in reducing plaque and gingivitis and preventing bad breath, alternatives may be preferable for individuals with sensitive skin or mucosa. Further research is needed to fully understand the long-term effects of SLS and to develop safer alternatives.

Disclaimer

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