It depends on cause
In medicine, we have common expressions that can mean a variety of medical diagnoses.
" is one of these things. It can be caused by a variety of things, each of which has a distinct treatment. The first thing to try would be over-the-counter creams (such as boudreaux's butt paste). If the rash won't clear quickly, the skin is broken, or the baby is under 3 months, he should see the dr.
Answer assisted by David Miller, Medical Student