The present invention is directed to a method for treating skin inflammatory diseases such as dermatitis, psoriasis, and acne, and rosacea, by administering 3-methanesulfonylpropionitrile or a pharmaceutically acceptable salt or solvate thereof to a subject in need thereof. The method alleviates the symptoms of the disease treated. The active compound can be administered by a systemic route or topical route. Topical administration is a preferred route of administration.