Hello, Welcome to Healthcare Magic, Chicken pox is a highly communicable 1-2 days before the appearance of rash and 4-5 days thereafter. After which virus tends to die out and looses the capacity to transmit disease to normal individuals. The scabbing usually begins 4-7 days after the rash and completed by 30 days. During the scabbing period you are child will be sterile and will not transmit disease to others. The disease will cause dehydration because of fever, the symptoms will come down once the rashes starts fading off. Your child should drink water as much as possible atleast 100ml/kg body wt./day. Thank you.