The disclosure relates to the use of an alpha-2 adrenergic receptor agonist and a pharmaceutically acceptable carrier for the manufacture of a medicament for treating or preventing psoriasis or a symptom associated therewith in a subject, wherein the medicament is for topical administration to a skin area of the subject that is, or is prone to be, affected by psoriasis or the symptom associated therewith, and wherein the alpha-2 adrenergic receptor agonist is brimonidine； and wherein the medicament may further comprise titanium dioxide in an amount that is sufficient to mask the color of brimonidine or another coloured ingredient in the formulation, and may be in a form selected from the group consisting of sprays, mists, aerosols, solutions, lotions, gels, creams, ointments, pastes, unguents, emulsions, and suspensions.
