How do i kno if my 3 yr old son has chickenpox?

Your doctor can ID.: A rash from Chickenpox often occurs first on trunk (chest/back) & then moves to face & then extremities. The rash becomes blisters that itch. Blisters usually have all transformed into scabs in about a week. There are usually around 100 to 300 lesions (more on adults than small children). The rash could spread to mouth, eyelids & genitalia.