A topical composition in the form of a serum for use in the treatment of psoriasis in a patient wherein said composition comprises: (a) about 75 wt% to about 99 wt% of a C 10 -C 30 carboxylic acid cholesterol/lanosterol ester mixture, based upon the weight of the composition less any solvent that may be present with a boiling point of 150°C or less; (b) about 0.01 wt% to about 15 wt% of a penetration enhancer selected from the group consisting of oleyl alcohol, lauryl alcohol, isopropyl myristate, oleyl oleate, levulinic acid, glycerol monooleate, methyl laurate, sorbitan monooleate, triacetin, cetyl alcohol, cetyl lactate, dimethyl isosorbide, dipropylene glycol, ethyl hexyl lactate, glycolic acid, lauramine oxide, lauryl betaine, lauryl lactate, lauryl laurate, isopropyl pamitate, myristyl alcohol, myristal lactate, octyl salicylate, oleamine oxide, oleic acid, oleyl betaine, salicylic acid, stearyl alcohol, stearyl lactate, triethanolamine triacetate and combinations thereof; (c) about 0.1 wt% to about 10 wt% of a water-insoluble film-forming/polymeric agent selected from the group consisting of polyalkenes, oleophilic copolymers of vinylpyrrolidone, acrylic copolymers, polyethylene glycol derivatives, polyolefins, polyurethanes and mixtures thereof; (d) about 0 wt% to about 10 wt% of an antioxidant; (e) about 0 wt% to about 10 wt% of a preservative selected from the group consisting of propyl paraben, methyl paraben, benzyl alcohol, benzalkonium chloride, tribasic calcium phosphate and phenoxyethanol or acids; (f) about 0 to about 25 wt% of a vitamin and wherein the treatment regimen consists of a topical administration of the composition to a psoriatic area of the patient at least once a day. (a) about 75 wt% to about 99 wt% of a C 10 -C 30 carboxylic acid cholesterol/lanosterol ester mixture, based upon the weight of the composition less any solvent that may be present with a boiling point of 150°C or less; (b) about 0.01 wt% to about 15 wt% of a penetration enhancer selected from the group consisting of oleyl alcohol, lauryl alcohol, isopropyl myristate, oleyl oleate, levulinic acid, glycerol monooleate, methyl laurate, sorbitan monooleate, triacetin, cetyl alcohol, cetyl lactate, dimethyl isosorbide, dipropylene glycol, ethyl hexyl lactate, glycolic acid, lauramine oxide, lauryl betaine, lauryl lactate, lauryl laurate, isopropyl pamitate, myristyl alcohol, myristal lactate, octyl salicylate, oleamine oxide, oleic acid, oleyl betaine, salicylic acid, stearyl alcohol, stearyl lactate, triethanolamine triacetate and combinations thereof; (c) about 0.1 wt% to about 10 wt% of a water-insoluble film-forming/polymeric agent selected from the group consisting of polyalkenes, oleophilic copolymers of vinylpyrrolidone, acrylic copolymers, polyethylene glycol derivatives, polyolefins, polyurethanes and mixtures thereof; (d) about 0 wt% to about 10 wt% of an antioxidant; (e) about 0 wt% to about 10 wt% of a preservative selected from the group consisting of propyl paraben, methyl paraben, benzyl alcohol, benzalkonium chloride, tribasic calcium phosphate and phenoxyethanol or acids; (f) about 0 to about 25 wt% of a vitamin and wherein the treatment regimen consists of a topical administration of the composition to a psoriatic area of the patient at least once a day.