Most formulations of magic mouthwash are intended to be used every four to six hours, and to be held in your mouth for one to two minutes before being either spit. Both adults and children can use magic mouthwash. Magic mouthwash is a treatment that some doctors prescribe to treat oral mucositis. Magic mouthwash is a prescription-only topical treatment with the power to ward off mouth sores. Magic mouthwash is typically compounded by a pharmacy and most often contains anticholinergic agents such as diphenhydramine (Benadryl); an anesthetic,. Magic mouthwashes are similar to other kinds of mouthwashes.