The itchy blister rash caused by chickenpox infection appears 10 to 21 days after exposure to the virus and usually lasts about five to 10 days. Other signs and symptoms, which may appear one to two days before the rash, include: 
Fever
Loss of appetite
Headache
Tiredness and a general feeling of being unwell (malaise)
 Once the chickenpox rash appears, it goes through three phases: 
Raised pink or red bumps (papules), which break out over several days
Small fluid-filled blisters (vesicles), which form in about one day and then break and leak
Crusts and scabs, which cover the broken blisters and take several more days to heal
 New bumps continue to appear for several days, so you may have all three stages of the rash — bumps, blisters and scabbed lesions — at the same time. You can spread the virus to other people for up to 48 hours before the rash appears, and the virus remains contagious until all broken blisters have crusted over. The disease is generally mild in healthy children. In severe cases, the rash can cover the entire body, and lesions may form in the throat, eyes, and mucous membranes of the urethra, anus and vagina.