A method for treating psoriasis by providing a pharmaceutical composition containing at least Ganoderma lucidum extract and administering a therapeutically effective amount of the composition to a patient in need thereof. Also disclosed is a method for treating psoriasis by first purifying Ganoderma lucidum extract into at least one fraction, then providing a pharmaceutical composition comprising at least one of the Ganoderma lucidum fractions, and administering a therapeutically effective amount of the composition to a patient in need thereof. A method for alleviating symptoms of psoriasis is disclosed. The symptoms of psoriasis are alleviated by providing a pharmaceutical composition containing at least Ganoderma lucidum extract and administering an amount of the composition effective to increase at least one of an IL-10 and IL-1Ra expression, whereby the symptoms of psoriasis are ameliorated.