Topical compositions and methods for treating psoriasis

1. A method of treating psoriasis, the method comprising topically applying a pharmaceutical composition to an affected area of a body of a subject suffering from psoriasis; wherein the composition comprises:

(a) halobetasol propionate at a concentration of 0.01 percent by weight of the composition;

(b) tazarotene at a concentration of 0.045 percent by weight of the composition; and

(c) an aqueous dermatologically acceptable carrier comprising carbomer copolymer type B, carbomer homopolymer type A, and a liquid oil comprising diethyl sebacate and light mineral oil;

wherein said applying is carried out one or more times per day for a period of time sufficient to treat such psoriasis and

wherein the composition comprising the halobetasol propionate and the tazarotene at said concentrations is capable of providing synergistic efficacy and synergistic reduction of at least an adverse event selected from the group consisting of itching, burning, and stinging in said treating.

2. The method of claim 1 , wherein said applying is carried out once per day for eight weeks.

3. The method of claim 1 , wherein the composition is an oil-in-water emulsion.

4. The method of claim 3 , wherein said halobetasol propionate and said tazarotene are dissolved in a component of said liquid oil of the oil-in-water emulsion.

5. The method of claim 3 , wherein said emulsion is a lotion.

6. The method of claim 3 , wherein said emulsion is a cream.

7. The method of claim 2 , wherein the method continues to provide relief to said psoriasis for a period of four weeks after said eight weeks of application of said composition.