Chickenpox is an infection with a blistering rash, which is caused by the Varicella virus. This virus also causes shingles.

The incubation period, the length of time from exposure to the virus to developing the condition, is two to three weeks. If someone in the house has chickenpox, the likelihood of someone else in the house catching it, who has not already had it, is as high as 90% - 9 out of 10.

Chickenpox usually affects children and starts with a slightly raised temperature, and feeling under the weather, along with the development of red spots, mainly on the body and face.

The spots appear over a few days and progress from being red spots to forming blisters, which eventually burst, dry, and crust, ultimately to heal. The spots are very itchy, and if the child scratches and infects them they will leave scars.

By the time the spots have stopped forming and are dried over and the temperature has fallen back to normal, the child is no longer infectious. Usually this takes about a week, until then they should remain off playgroup or school.

Chickenpox does not usually make children very ill, and for most the main problem is the itchiness. Your doctor will not normally need to see the child, but you should let him know that the child has had it. Occasionally more serious complications can occur, and if a child does not appear to be following the above course it is worth speaking to your doctor.

Having had chickenpox most people are immune and can not catch it again. However the virus particles remain dormant in your nervous system and can, at a later stage, cause shingles. As a result of the large numbers of people who catch chickenpox as children, 90% of adults are immune.

Many people find that calamine lotion helps to soothe the itch. Paracetamol liquid helps to ease any aches and pains, and also keeps down the temperature.

People with chickenpox or shingles should stay away from others who have not had chickenpox until their rashes have dried up. This especially applies to staying away from people who have depleted immune systems (including people: on steroids; on cancer drugs; on immunosuppressant drugs for transplants; or with AIDS). These people are said to be immunocompromised and cannot fight off an infection as well as the rest of us. Another group who are at higher risk is pregnant women and newborn babies.

There is now a chickenpox (varicella) vaccine. This is not used in all countries. It can be given as a protective measure to immunocompromised people, especially children with leukaemia or organ transplants.

For people who are not immune and who are exposed to the virus, there is a way of using the antibodies that someone else has made against an infection. This is called passive immunisation.

An injection is made up from the protein in people's blood which fights off infections (immunoglobulin). In the case of chickenpox it is made from pooled serum from blood donors who have recently had chickenpox or shingles. In the UK it is standard practice for all blood donors to be tested for, and be clear of HIV, Hepatitis B, and Hepatitis C.

This product is known as Human Varicella-Zoster Immunoglobulin (VZIG). Its supplies are limited, as a result of the small number of suitable donors, and thus it can only be given to those at greatest risk and in whom it has been shown that it is likely to be effective.

VZIG is recommended for use in people who fit into all three of the following groups:

1. A clinical condition that increases the risks of developing a severe response to the varicella virus, such as:
   • Immunocompromised (people on steroids; on cancer drugs; on immunosuppressant drugs for transplants; with AIDS; etc.)
   • Newborn babies
   • Pregnant women
2. No antibodies to varicella-zoster virus
3. Significant exposure to chickenpox or shingles

If any of these people develop chickenpox it is likely that the doctor will arrange hospital admission, or at least ask a specialist to see them. In such infections anti-viral drugs may be used.

• Care calamine lotion
• Calpol paracetamol suspension