That is really something about an allergy to Benadryl. My son had an allergic reaction to something else which he said was in the form of a big red pill that started with a "T" (He couldn't remember what). It happened at 2am and was alone when his tongue swelled up to the point of having difficulty breathing and couldn't talk. He managed to call my daughter who somehow figured out the grunts and coughing sounds on the phone were those of her brother and took him to the emergency room. What they gave him were two shots of Benadryl and told him that if it happened again to just take Benadryl! So it seems that it's important to find out what possible reactions there are to anything that goes in the body and how to counteract them if need be. And make sure the doctor knows everything that is being taken.