Chickenpox causes a characteristic itchy, red rash of blister-like spots that usually appear first on the face, scalp, chest, and back, and may then spread all over the body. The rash usually appears around two weeks after first exposure to the varicella virus and begins as small, red bumps that look like pimples. The bumps soon become blisters filled with fluid that then break open and crust over; the entire process takes between five and ten days. New bumps continue to appear for a week or so, sometimes hundreds in total, even as the existing bumps are crusting over.

The rash may be preceded or accompanied by other symptoms including:

• mild cough and runny nose
• fever
• abdominal pain
• mild headache
• malaise or irritability

Chickenpox is usually a mild disease, especially in children. It usually lasts a total of one to two weeks and rarely leads to complications, though when complications do occur they can be quite serious. Possible complications include bacterial infection of the skin, inflammation of the brain (encephalitis), and pneumonia. If a person is not exposed to varicella until adolescence or adulthood, they are at increased risk of severe disease and complications are more likely to occur.

While most people who have had chickenpox will be immune to the disease and are unlikely to get it again, there is a small possibility of the virus reawakening and causing a painful disorder called shingles.