Immunisation can help prevent the spread of chickenpox.

Chickenpox causes a rash of red, itchy spots that turn into fluid-filled blisters. They then crust over to form scabs, which eventually drop off.

Your child is likely to have a fever at least for the first few days of the illness and the spots can be incredibly itchy, so expect them to feel pretty miserable and irritable while they have chickenpox.

Some children have only a few spots, but in others they can cover the entire body.

The spots are most likely to appear on the face, ears and scalp, under the arms, on the chest and belly and on the arms and legs.

The incubation period for chickenpox is between 10 and 21 days. You are infectious from up to 2 days before the red spots appear and until around 5 days after all scabs or crusts are dry.

Chickenpox can be severe at any age and have serious complications. Complications include:

• bacterial skin infections
• pneumonia
• swelling of the membranes covering the brain (aseptic meningitis)
• decrease in blood platelet cell (thrombocytopenia)
• bleeding problems
• infection of the blood (sepsis)
• inflammation or infection of the brain (encephalitis)
• trouble with balance and co-ordination (cerebellar ataxia)
• foetal abnormalities in pregnant women (see below)
• dehydration

Pregnant women should be especially careful to avoid chickenpox as it can affect the unborn baby by causing foetal malformations, skin scarring and other serious problems (congenital varicella syndrome).

There is no specific treatment for chickenpox, but there are medicines and pharmacy products which can help alleviate symptoms, such as:

• paracetamol to relieve fever
• calamine lotion and cooling gels to ease itching

In most children, the blisters crust up and fall off naturally within one to two weeks.

Adults who have had chickenpox as a child may also get shingles later in life, as they are both caused by the virus varicella zoster.