On the first day a rash appears as small red patches about 3-4mm across. Within a few hours of these developing, small blisters appear in the centre of these patches. During the next three or four days further patches will appear and the earlier ones will turn ‘crusty’ and fall off. Oily calamine lotion may be applied to soothe the often severe itching. Cool baths may also help. The most infectious period is from two or three days before the rash appears and up to five days after this date. Children may return to school as soon as the last ‘crusts’ have dropped off.