Hello, I am not sure what allergic reaction your mother to the eptoin (phenytoin) requiring the drug to be stopped and starting prednisolone for the rash. Phenytoin can cause a severe drug induced systemic reaction called Drug rash, Eosinophilia, Systemic Symptoms (DRESS for short) where there is fever, big glands, skin peeling off and liver problems. Other drugs implicated in DRESS should ten be avoided. I am certain your mother did not have this...but maybe just a rash that can be itchy and known as urticaria. Prednisolone is occasionally used a last resort but antihistamines are more than effective in treating urticaria. The alternative antiepileptic is a good choice, and suggest you discuss with your Neurologist in tapering and stopping the steroids after 5 days if the diagnosis was not DRESS. I hope this was helpful. Best Wishes.