A hygroscopic pharmaceutical composition includes at least one hygroscopic substance at a concentration sufficient to provide an Aw value of at least 0.9 and an antiinfective agent. A foamble pharmaceutical carrier includes about 50% to about 98% of a polar solvent selected from the group consisting of a polyol and PEG； 0% to about 48% of a secondary polar solvent； about 0.2% to about 5% by weight of a surface-active agent； about 0.01% to about 5% by weight of at least one polymeric agent； and a liquefied or compressed gas propellant at a concentration of about 3% to about 25% by weight of the total composition.
