Use warm water when showering rather than hot water. Warm water will be more soothing to the skin.
Turn your back to the shower so the water does not hit your breast directly.
Be conscious of areas where sensitive skin might rub together and try to avoid rubbing, if possible. These areas may include armpits, the area under your breast, or along your cleavage.
Use cornstarch powder or baby powder to reduce friction in the armpit and other areas that rub.
Stay out of the sun -- it can make sensitive skin feel worse. If you do go outside, be sure to cover up and use sunscreen.
Don’t wear a bra or prosthesis if the skin around your breast area is sensitive.