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A rash under the breast usually results when the lower part of the breasts rests against the skin below and traps moisture or perspiration which then becomes breeding grounds for bacteria, fungus and other infections.
 One of the most common causes of under-breast rashes is cutaneous candidiasis. It’s a yeast infection that can appear anywhere on your body, but it usually targets under the breast
Keep undersides of your breast as dry as possible.
Apply deodorant under breast to reduce sweating.
Place a piece of cotton below breast to absorb moisture.
Control your sugar levels.
Wear light clothing
Use supportive bras which are able to lift your breasts.
Thoroughly rinse your bra to remove any residual detergent chemical in it.
Use calamine lotion several times a day.
Apply a combination of hydrocortisone cream and lotrimin cream in the night.

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