I have dark spots under both breast looks like a bruise have not been hurt or been in any accident currently not allergic to anything what can it be?

Dark spots?: Women who are allergic to the metal in an underwire bra can sometimes develop chronic discoloration to the skin. The reaction is caused by allergy to nickel. This is a contact dermatitis (which is different than an environmental allergy). I might suggest an over the counter topical steroid cream and using a plastic underwire bra (if you were them).