Treatment of psoriasis typically involves a combination of topical treatments, phototherapy, and oral or injectable medications. Topical treatments include corticosteroids, vitamin D analogues, retinoids, coal tar, anthralin, and salicylic acid. Phototherapy involves exposing the skin to ultraviolet light, either from natural sunlight or from artificial sources. Oral or injectable medications include methotrexate, cyclosporine, biologic agents, and apremilast.