Abstract: The present invention relates to a novel pharmaceutically active composition which is able to permeate into the deeper layers of the skin and the keratin sheets of nails. The composition is a microemulsion comprising at least an alcohol ethoxysulfate, an ethoxylated glyceryl fatty acid ester, and an ethoxylated sorbitol or sorbitol anhydride fatty acid ester. The composition may optionally comprise further additives like emollients, substances for hardening a nail, or substances for enhancing nail growth. The composition is particularly suitable for treating fungal infections of the skin or nails, such as athlete's foot and onychomycosis. The composition is also suitable for treating inflammatory skin diseases, such as psoriasis and atopic eczema.