Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. It could be either an adverse drug reaction to some oral drug or it could be a hypersensitivity reaction to a virus or a drug. Perhaps if you could have uploaded images it would have helped me greatly. I suggest him to take an oral antihistamine e.g Cetrizine tab once every evening. He may begin with application of cortisone cream, however, if the rash worsens or doesn t improve then he might have to visit a doctor personally. Hope I have answered your query. Let me know if I can assist you further.