The present invention relates to methods for disinfecting or decontaminating a material or for preventing an infection or contamination of a material. The invention further relates to compositions which are suitable for disinfecting a material or for preventing an infection or contamination of a material and to uses of such compositions. The invention further relates to a medical use of chitosan and to a pharmaceutical composition comprising the chitosan. The invention further relates to a method of treating a microbial infection and to an aqueous solution comprising chitosan. The invention moreover relates to a chitosan or a pharmaceutical composition comprising a chitosan for an epithelial cell growth stimulating treatment of a patient's tissue and to a method of stimulating the growth of epithelial cells. The invention also relates to a tissue dressing material.