A composition for topical administration to an external body surface comprising: a polyhydroxy acid and a zinc salt of its conjugate base, wherein the polyhydroxy acid is selected from lactobionic acid, gluconolactone, a combination of lactobionic acid and gluconolactone and derivatives thereof； a partition coefficient enhancer selected from propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, 1,5-propane diol, propylene carbonate, dipropylene glycol, a glycol ether, diethylene glycol monoethyl ether, a pyrrolidone, N-methyl pyrrolidone and a combination thereof； a diffusion coefficient enhancer which is selected from a C12 to C14 straight chain fatty acid or a C14 straight chain primary alcohol and wherein the composition has a pH in the range of 2.7 to 5. The diffusion coefficient enhancer may be 1-tetradecanol. The zinc salt may be formed from zinc oxide. The composition may also comprise an emollient such as mineral oil, petrolatum, paraffin, hydrogenated polydecane, hydrogenated didecane, hydrogenated polyisobutene. The composition may also comprise a further acid, such as citric acid. The composition may also comprise a surfactant, which may be a surfactant system comprising methyl glucose sesquistearate and PEG-20 methyl glucose sesquistearate and optionally glyceryl stearate.
