The present invention relates to the use of osmolytes for treating allergic or viral respiratory diseases, e.g. allergic rhinitis (hay fever) as well as rhinovirus and/or adenovirus infections. The invention also relates to a medicament preparation containing one or more compounds from the group of osmolytes. The group of osmolytes used in the invention comprises various low-molecular substances, more specifically ectoine, 4,5,6,7-tetrahydro-2-methyl-1H-[1,3]-diazepine-4-S-carboxylic acid (homoectoine), hydroxyectoine, di-myo-inositol-phosphate (DIP), to cyclic 2,3-diphosphoglycerate (cDPG), 1,1-diglycerol phosphate (DGP), β-mannosylglycerate (firoin), β-mannosylglyceramide (firoin-A), dimannosyl-diinositol phosphate (DMIP), glucosylglycerol, taurine, betaine, citrulline, and/or a derivative, e.g. an acid, salt, or ester of said compounds.