Chickenpox is an illness caused by the varicella-zoster virus. This virus is highly contagious and can spread through direct contact with the rash or when a person with chickenpox coughs or sneezes and you breathe in the air droplets. The rash caused by chickenpox appears 10 to 21 days after exposure to the virus and often lasts about 5 to 10 days. Other symptoms that may appear 1 to 2 days before the rash include fever, loss of appetite, headache, tiredness, and a general feeling of being unwell. Once the chickenpox rash appears, it goes through three phases: raised bumps called papules, which break out over a few days, fluid-filled blisters, and finally, scabs that form over the blisters and fall off.

Chickenpox is most common in children under the age of 10, but it can be caught at any age. Children usually catch chickenpox in winter and spring, particularly between March and May. Chickenpox is infectious from 1 to 2 days before the rash starts and stops being infectious when all the blisters have crusted over, which usually happens 5 to 6 days after the start of the rash. Once you have had chickenpox, you usually develop antibodies to the infection and become immune to catching it again. However, the virus that causes chickenpox, the varicella-zoster virus, stays inactive in your body’s nerve tissues and can come back later in life as an illness called shingles.