Hi, I Have Many Hive-like Red Raised Itchy Spots Confined

Hi, I have many hive-like red raised itchy spots confined to my left arm both on the upper and lower inside and outside of arm with some extending to the shoulder. This is day two, with them getting larger, redder and more itchy. Spouse suggests "bed bugs", I refute. Would this not be all over body, not simply confined to one arm? No recent hotel stays either. Have taken oral benedryl; no relief.