Seven year old boy with chickenpox. Chickenpox is a highly contagious viral infection. It spreads easily from person to person and is most common in young children. The main symptom is an itchy, spotty rash with small blisters that can spread over the entire body. For most people, chickenpox isn't serious and will heal on it's own within a couple of weeks. Symptoms can be eased with cooling creams and painkillers.