Disclosed herein is the use of 2,3-dimethyl-6-(N,N-dimethylaminoethyl)-6H-indolo-(2,3-b)quinoxaline (B-220) or a pharmaceutically acceptable salt for the manufacturing of a medicament for use in the treatment of herpes virus infections of the skin or mucous membranes in a mammalian subject by topical administration of a therapeutically effective dose of said medicament to the skin or mucous membrane of the mammalian subject.