Aqueous Cream and SLS
Emollients (moisturisers) soothe, hydrate and protect the skin. Long-term emollient therapy is the main treatment for dry skin conditions (xerosis, ichthyosis and eczema). Emollients should be unperfumed and prescribed in adequate quantities and in a formulation (cream, ointment, oil, soap substitute) acceptable to the user.
Aqueous cream (AC) has been used for 60 years as a prescribed and OTC (over-the-counter) light emollient and as a ‘wash-off’ soap substitute and hand wash. AC is an oil-in-water emulsion (rather than a greasy water-in-oil emollient like paraffin-based ointments). There are five aqueous cream products currently licensed in the UK (Pinewood, Ayrton Saunders, Thornton and Ross, Ecolab, Boots). They all have sodium lauryl sulphate (SLS at a concentration of 0.9%) as an ingredient.
When used as a ‘leave-on’ moisturizer, aqueous cream may cause skin reactions, especially in those with eczema or inflammed skin. In one study of 71 children with eczema, over 50% developed immediate (within 20 mins) burning, stinging, itching and redness. As a result, NICE and other guidelines advise that AC can be used as a wash product but not as a leave-on moisturizer.
The irritation associated with AC is thought to be caused by SLS, a component of emulsifying wax, which is an ingredient of AC. SLS is produced from coconut or palm oil and in low concentration acts as an emulsifier (keeps oil dissolved in water) and at higher levels is a detergent (foams up and removes grease and oil) and antiseptic. It helps to maintain the creamy consistency of emollients, cosmetics and toothpaste. In higher concentration, up to 10% in shampoo and bubble bath, it produces foam. In domestic cleaning products, where SLS concentration may reach 15% or more, it acts as a strong detergent.
The mild detergent effect of SLS, even at low concentration, may underlie the skin irritation caused by AC in some people and even mouth ulcers from SLS-containing toothpaste. Some researchers have used concentrations of 2% SLS to test for skin sensitivity and in general have reported that the face is more likely to be affected, especially in people with a history of eczema and asthma. Preservatives in AC, eg. phenoxyethanol and parabens, may also cause adverse skin reactions.
AC labels and information leaflets should contain a warning of potential local skin reactions and SLS should be listed separately as an ingredient.
Some journalists have published and posted alarming articles about the dangers of SLS in recent years. They have described it as an industrial detergent and caustic floor cleaner but generally failed to point out the difference in concentration of SLS in various products. Claims that absorption of SLS through the skin can damage the eyes, cause toxic damage to internal organs and even increase cancer risk are not backed up by credible evidence and one of the original investigators later withdrew his claims about eye damage. The cancer-risk of any chemical is always difficult to assess but it is reassuring that the FDA (Food and Drug Administration) in the USA does not regard SLS in skin care products, shampoos and toothpaste as posing a cancer risk. The FDA also allows SLS as a food additive. It is possible that some of the scary stories about SLS are put out by people selling ‘natural products’!
Article written by Consultant Dermatologist on ISG Medical Advisory Board