Anti-irritants II: efficacy against cumulative irritation

The Allergy Center, Odense University Hospital,University of Southern Denmark, DK-5000 Odense C, DenmarkSo-called anti-irritants (AI) are widely used in cosmetic formulations, with the aim of reducingirritation from substances in the formulation. It may also be claimed that they are ‘soothing’ and‘healing’ ingredients. However, the proof for these claims is circumstantial. The dose–responseeffect of 4 alleged AI (nifedipine, (-)-a-bisabolol, canola oil and glycerol) was studied on experi-mentally induced acute irritation in healthy volunteers, and only glycerol showed dose-related response and effects potentially better than no treatment. The acute irritation modelonly allowed a small window of opportunity in which to demonstrate efficacy. Therefore, theeffect of AI was studied in a cumulative irritation model by inducing irritant dermatitiswith 10 min daily exposures for 5 + 4 days (no irritation on weekend) to 1% sodium laurylsulfate on the right and 20% nonanoic acid on the left volar forearm. AI ointments were appliedtwice daily. Clinical scoring was performed daily, evaporimetry (Trans Epidermal Water Loss),hydration and colourimetry were measured at baseline (D0), in the middle and at the end oftreatment. The glycerol ointment was the only treatment statistically better than both ‘no treat-ment’ and vehicle.Key words: anti-irritant; bisabolol; canola oil; cumulative test; glycerol; human; in vivo; nifedipine;nonanoic acid; skin irritation; sodium lauryl sulfate.