Chickenpox. Close-up of vesicles (lesions) on the skin of a chickenpox patient. Chickenpox (or varicella) is a common infectious disease of childhood. The disease is characterized by headache, fever and malaise followed by eruption of a rash over most of the body. The rash (as seen here) appears in crops and consists of clusters of small, red, itchy spots that become fluid filled blisters, 2 to 3mm in diameter, within a few hours. Rest is usually all that is needed for a complete recovery. Calamine lotion can be used to ease the itchiness and paracetamol taken to reduce fever. The disease is more serious in adults or children on immunosuppressive drugs.