The present invention provides a photosensitising composition comprising a mixture of at least one oxygen carrier, at least one oxidising agent and at least one surfactant, and its uses. The ratio of the at least one oxygen carrier to the at least one oxidising agent to the at least one surfactant may be in the range of 50:40:10 to 80:19.8:0.2. The photosensitising composition may be used for treating and/or preventing conditions caused by microorganisms.
