Prednisone is a corticosteroid medication which can be used as an immunosuppressant. Doctors prescribe it to treat many different conditions, such as arthritis, severe allergies, multiple sclerosis, lupus, cancer, Crohn`s disease, asthma, adrenocortical insufficiency, pericarditis, myasthenia gravis, nephrotic syndrome, migraine, cluster headaches, thyroiditis, laryngitis and various other conditions which have not been listed here.