A Small Clump/rash Of What Looks Like Poison Ivy Appeared

A small clump/rash of what looks like poison ivy appeared on my right bicep four days ago. The area is about 1" in diameter and consists of raided red spots with some swelling under the skin around the bumps. Two days ago more small red bumps appeared on my right forearm and on the back of my right shoulder. Coincidental with the appearance I began experiencing discomfort under the skin on my right arm and in my right hand and shoulder. No strain that I know of. Have not been around any plants but I do have pets. I have been treating with a topical antihistamine. Any thoughts?