Effects of sorbitan sesquioleate on non-immunologic immediate contact reactions to benzoic acid

In order to study the effects of an emulsifier on non-immunologic immediate contact reactions, 500, 250, 125, 62, and 31 mM benzoic acid (BA) was tested in 12 medical students on a skin area of the upper back treated with sorbitan sesquioleate in yellow petrolatum (20:80) 3 times daily for 2 days and on a contralateral skin area treated with petrolatum. The test areas were visually observed and the changes in the skin blood flow were monitored using laser-Doppler flowmetry 40 min after application. The reactions to 250 and 125 mM BA in petrolatum were stronger on the skin area treated with sorbitan sesquioleate than on the reference site treated with petrolatum. In visual observation and in laser-Doppler flowmetry, BA in the mixture of sorbitan sesquioleate and petrolatum (20:80) produced weaker reactions than in petrolatum, both on the sorbitan sesquioleate treated skin site and on the site treated with petrolatum.