Surfactants is the portmanteau of “surface active agent” and is an umbrella term for chemicals with properties that allow water and oils to mix, as well as form foam. This property is extremely useful in preparation of detergents from cosmetics to machine cleaning. Surfactants are naturally present throughout nature but can also be produced or made from petroleum and other oils. Sodium-lauryl sulphate (SLS) is a very well-known surfactant additive in cosmetics and everyday household cleaners. In Europe mainly sodium-lauryl ether sulphate (SLES) is used due to safety concerns of the former surfactant. These surfactants are present in toothpastes and mouthwash where its main goal is to help in dispersal of active agents around the mouth as well as help remove bacteria or food stuff. SLS and SLES can be made from petroleum, plant oils (palm oil, coconut oil) which carry their own environmental burden, but additionally SLS has also been implicated with some adverse effects in some people. Therefore, SLS has been demonised in the mainstream and a lot of misinformation may be popularised.
First and foremost, SLS is considered safe in oral health care preparations at the amounts that are typical and totally safe from a risk assessment perspective. However, clinical case studies as well as several dermatological experiments indicated potential for allergenicity (allergic reaction causing), and general irritation. There has also been some evidence that SLS can disrupt healing processes for example in the case of ulcers. The rate of the susceptibility to SLS related issues on a population level have not been explored and the mechanism is not fully understood. Less research has been dedicated to SLES, but it is generally accepted that it is less of an irritant than SLS. How our indigenous oral bacteria interact with either surfactant is also not entirely clear. Despite that, SLS or SLES are present in nearly all toothpastes and coveted for the foaming sensation it brings.
Addition of these synthetic surfactants may be another case of where large pharmaceuticals and cosmetic producers have considered the efficacy of the chemical secondary to the biophysical properties it brings to the cosmetic preparation. The evidence is not clear whether the presence of surfactants is at all beneficial to oral health outcomes (plaque prevention, gum health etc.). For example, randomised clinical trials have highlighted no significant differences in using SLS or SLS-free toothpastes.
Surfactant-free toothpastes or dental tablets are not in the majority. Reuterdent dental tablets do not contain surfactants except those that may be produced by the symbiotic bacteria L. reuteri in small quantities. More evidence is needed to support a net beneficial effect by SLS or SLES on oral health and reports of possible allergenicity or irritation are of some concern. The potential environmental burden of sourcing SLS not produced from petroleum or palm oil can also be complex. Hopefully further research will shed light on how or why surfactants can be problematic for some individuals. If it turns out they are essential for good oral health, then hopefully this work can also help develop greener process designs in manufacturing these kinds of surfactants.