This invention relates to a formulation for use in the. topical treatment of diseases caused by pathogen micro- organisms and/or parasites in animals, comprising sodium dodecyl sulphate, 2, 2, 2-trichloroacetic acid and a stable colloidal suspension of (nano-) particles, of iron (III). The invention further relates to a process for the manufacture of a formulation, and uses of the same formulation and its components.