Chickenpox may start out seeming like a cold: You might have a runny or stuffy nose, sneezing, and a cough. But 1 to 2 days later, the rash begins, often in bunches of spots on the chest and face. From there it can spread out quickly over the entire body — sometimes the rash is even in a person’s ears and mouth. The number of pox is different for everyone. Some people get just a few bumps; others are covered from head to toe. At first, the rash looks like pinkish dots that quickly develop a small blister on top (a blister is a bump on your skin that fills up with fluid). After about 24 to 48 hours, the fluid in the blisters gets cloudy and the blisters begin to crust over.
Chickenpox blisters show up in waves, so after some begin to crust over, a new group of spots may appear. New chickenpox usually stop appearing by the seventh day, though they may stop as early as the third day. It usually takes 10–14 days for all the blisters to be scabbed over and then you are no longer contagious.
Chickenpox is most common in children who are between two and eight years of age, although you can develop chickenpox at any age. You are infectious from about two days before the rash appears until roughly five days after. Therefore you or your child should stay at home until all of the blisters have fully crusted over, and this usually happens five to seven days after the first blister appears. After the last blister has burst and crusted over, you are no longer infectious.