Healthy persons are invited to participate in the study and are given a home protocol (WURSS21), nasal spray and a sample pin. The included persons are told to make a nasopharyngeal sampling from the nose when they are sure that they have caught a common cold. After the sampling they start to spray and also fill in the records daily. The aim of the study is to investigate whether a nasal spray with glucose oxidase could shorten an episode of common cold.