A mild but highly infectious condition, chickenpox causes an itchy rash that blisters and then crusts over.
Most common in children under ten years of age, chickenpox is so common in childhood that 90% of adults who grew up in the UK are now immune as they have had it before.
Chickenpox can cause serious complications for pregnant women and their babies and so it is vital that children suffering from it remain away from nursery until they are clear.
There is no cure for chickenpox although symptoms can be relieved through painkillers and calamine lotion. In most people, the blisters crust up and fall off naturally within one to two weeks.
The most common symptom is the red rash that covers the body. Some people may only have a few spots but in others it may cover the whole body. It may appear behind the ears, on the face, over the scalp, under the arms, on the chest and stomach or on the arms and legs.
It starts as small, itchy red spots. After 12-14 hours they develop into blisters which are intensely itchy.