Red spots under both breasts?

Intertrigo: Intertrigo (intertriginous dermatitis) is an inflammatory condition of skin folds, induced or aggravated by heat, moisture, maceration, friction, and lack of air circulation. Intertrigo frequently is worsened or colonized by infection, which most commonly is candidal but also may be bacterial, fungal, or viral. Intertrigo commonly affects the axilla, perineum, inframammary creases, abdominal folds.

Unsure.: Intertrigo is one possibility. This rash would likely need to be examined and more history obtained to be able to provide you with useful input about the diagnosis or possible treatment.