A foamable pharmaceutical composition comprising a corticosteroid, a quick-break foaming agent, a propellant and a buffering agent, sufficient to buffer the composition to within the range of pH 3.0 to 6.0 is disclosed. The quick-break foaming agent typically comprises an aliphatic alcohol, water, a fatty alcohol and a surface active agent. Due to the nature of the compositions of the invention, they are especially well-suited for use in the treatment of various skin diseases, and in particular, in the treatment of scalp psoriasis.