We can only speculate at the cause of your sub mammary rash
as it will need physical examination to ascertain the real cause and remedy. we could think of these causes like heat (Seborrheic Dermatitis
and Dry skin
. This may be due to maceration because of poor support and/or bacteria and/or yeast growing there. Treatment of the bacteria and/or yeast are necessary to bring the problem under control, but you must take special precautions to clean under your breasts thoroughly, dry with a clean towel, then blow dry the area under your breasts where the dermatitis is located with a hair dryer. This should then be followed by application of a topical (that is applied over the area as a cream or lotion) antibiotic and/or topical anti-yeast preparation. You should wear a good bra and put a towel under your breasts at night so that any perspiration is wicked away. You see a Family Physician to get the topical creams applications.
In younger individuals who develop this problem, it is often associated with being overweight
and possibly being diabetic. Your primary physician and/or dermatologist
should take all of this into account.