If the chicken pox is not bothering him then let it be. It is important that the natural immune system which temds to be suppressed these days from vaccinations gets to learn how to do its job. It is noticeable that children, when allowed to have a childhood disease without suppression have a growth spurt physically and mentally ( just ask their teacher) soon after the disease.

When itching is a problem I always prescribe Rhus Tox 30C, one dose and repeat only when needed. This usually does the trick. But it can be other remedies which is why you will have to let us know if there is a problem and how it affects him. Nothing should be given prophylactically