Chicken Pox Condition_symptoms How Can You Tell The Difference Between Chicken Pox And Allergic Reactions?

How can you tell the difference between chicken pox and allergic reactions? - chicken pox condition_symptoms

I am a son aged 13 months, I just observed to have stains on the face and whole body (like chicken pox), but have a rash on his private life and Butt I erythema rash, but does not work. I'm still not sure whether his reaction ALLERIC smallpox or chicken. He eats and plays and has no fever.