Since your son has a rash
around the anus, there are various possibilities which need to be ruled out.
Infections especially fungal infections are the most common cause of the same but treatment with antifungals has not been able to help.
Allergic skin reactions are another important reason for the same.
Even deficient minerals especially zinc are an important cause and proper evaluation of the child is essential to look for the main reason of this presentation.
Dr Geetika Paul