Suggest Remedy For Rashes On Face Of A Teenager

I have a 13 year old son that has developed a rash on his face. This has been happening since Christmas and it is getting worse. It looks like an allergic reaction but we are not sure. The rash does not itch. Could you give us some suggestions? He is taking a low dose of predisone for 4 days. We are on day 3 and not seeing any differences.