I am a 35 year old female, 5'10, 160lbs, with no serious medical history (tonsilitis at around age 6 or 7, no other hospitalizations ever). I have a single welt that reappears every few days on my left breast. It usually lasts no more than 30 minutes, does not itch or feel sore, and disappears without a trace...only to come back a few days later. Should I be concerned?