My son just recently developed a rash all over his body. he just finished antibiotics for strep throat two days ago. is this normal?

Sounds like allergy: It sounds like your son may have developed an allergy to the antibiotic. You should go back to the doctor to confirm this. Although antihistamines like Benadryl (diphenhydramine) or zyrtec will help with itching, symptoms like wheezing, difficulty breathing, swallowing trouble or swelling in the face or mouth are very concerning and should be addressed by a doctor right away.

Allergic Rash: I think your on is probabely has allergic rash due to antibiotcs.You should check with your pediatrician asap, so that it can be confirmed and it goes in his record that he is allergic to the antibiotic he was prescribed, so that he is not prescribed the same again.

Possible mononucleos: It could be that he has developed and allergy to the antibiotic he was treated with. If he was on penicillin or Amoxicillin you can get a significant rash if you have mononucleosis when treated. That does occasionally happen. Check with your dr.

Rash: I agree allergy is on the list of issues. However if he got Amoxicillin and had a viral illness rather than a bacterial one, the rash is not allergic. Further the rash might be related to the strep throat, in the form of a sandpaper texture suggesting scarletina.