A Physicochemical Approach to Minimize the Irritant Capacity of Anionic Surfactants

Skin care companies try to find the best way for cutaneous hygiene in defective skin conditions. Novel strategies to ensure extra-mild non-soap surfactant cleansing products should be searched for and designed. Among possible strategies, the control of the physicochemical behaviour of surfactants in solution seems to be a promising approach to minimize their irritant properties. To assess this, we have tested – with 28 healthy volunteers by means of 48-hour patch testing – the irritant capacity of the following solutions: sodium lauryl sulphate (SLS) 1% w/w, disodium cocoyl glutamate (SCG) 1% w/w, sodium PEG-4 lauramide carboxylate (SLC) 1% w/w and the mixtures SLS 1% w/w + SCG 1% w/w and SLS 1% w/w + SLC 1% w/w. The cutaneous responses were evaluated by visual scoring and bioengineering measurements of transepidermal water loss, laser Doppler cutaneous blood flow and skin colour reflectance. The experimental values of all bioengineering end-points and visual scores have shown that the addition of co-surfactants to a constant dose of SLS produces a significant reduction of skin irritation notwithstanding an increase in the total surfactant concentration. The physicochemical studies show that the control of the physicochemical behaviour of surfactants in solution could be a promising approach to develop cleansing products with a less damaging effect on the skin.