I have reddish blotches on my abdomen and under breasts. no longer itchy, and no other symptoms whatsoever. hives? how long do they last?

Hives / Urticaria: It's impossible to diagnose a rash from a short description. Hives generally itch quite a bit, and they are raised like mosquito bites, so you can feel definite bumps when you rub the skin. Under the breasts, it may be more likely to be a heat rash or mild Candida. Those rashes aren't always itchy. If it was previously itchy and IS hives, it resolves in a few hours and the skin looks perfect.