Chickenpox is a highly contagious infection. It causes an itchy rash, consisting of small, raised, blistered or crusted spots.
Chickenpox is a common infection caused by the varicella zoster virus. It’s most commonly seen in children under 10, but you can catch it at any age. Once you have had chickenpox, you’re very unlikely to catch it again.
For most people, chickenpox usually goes away after a week or so. Once your symptoms have cleared up, the virus stays dormant in your body for the rest of your life. At any time later in life, the virus can be reactivated. This causes shingles, which is a related disease caused by the same varicella zoster virus.
You can catch chickenpox at any time throughout the year, but it’s most common in winter and spring.
There is a very small chance that you can get chickenpox more than once, especially if you have a weakened immune system (for example, you have HIV/AIDS or are taking medicines that suppress the immune system).
If you become infected with the chickenpox virus, you will begin to get symptoms 10 to 21 days later. Initial symptoms of chickenpox include:
A day or two after the first symptoms begin, you will develop a flat rash with small fluid-filled blisters or spots.These fluid-filled spots are usually very itchy and vary in size. You will usually get spots on your face and scalp first, which may then spread to your chest, arms and legs. You may also get spots inside your mouth and nose.
Your spots might develop into pustules (blisters containing pus). These blisters will usually crust over within a few days to form scabs. Your spots usually take around two weeks to heal completely. They don’t usually leave a scar, unless they get infected. This can happen if you scratch them.
The severity of chickenpox infection varies – it’s possible for children to be infected but show no symptoms. If you’re an adult, your chickenpox may be more severe. The rash may be more widespread and you may have a fever for longer.
These symptoms aren’t always caused by chickenpox. If you’re in any doubt, speak to your GP or seek advice from a pharmacist. It’s usually best not to go to your GP surgery if it can be helped, because chickenpox are so contagious.
If you're generally healthy, chickenpox is usually a mild infection and serious problems are rare. Chickenpox can be more serious for adults, babies or children who have a weakened immune system. For example, if you have HIV/AIDS or are taking medicines that suppress your immune system.
Occasionally, healthy people get other problems from having chickenpox. For example, your rash or spots could become infected. This may delay the healing process and can leave you with scars.
The most frequent and dangerous complication of chickenpox is pneumonitis (inflammation of your lung tissue). You’re more likely to get this if you smoke.
Sometimes, although it’s rare, chickenpox can cause encephalitis (inflammation of your brain) or pneumonia (an infection in your lungs).
At any time later in life, the varicella zoster virus can be reactivated. If this happens, you will develop shingles. Shingles causes a blistering rash that usually appears on one side of your body. It can be very painful. You can’t develop shingles from exposure to a person with chickenpox. However, you can develop chickenpox as a result of exposure to the fluid from shingles blisters if you haven’t had it before.
Chickenpox is highly contagious. If you come into contact with someone who has chickenpox and you haven’t previously had it, you have a very high chance of catching it.
Chickenpox is transferred through direct person-to-person contact, usually through the air when you cough or sneeze.
The incubation period (the time from when you become infected to when your symptoms first appear) is between 10 and 21 days. The most infectious period is one to two days before the rash appears. However, you can still catch it from someone until all the spots have crusted over. This is usually about five to six days after the onset of the chickenpox rash.
In most cases, you can diagnose chickenpox from its characteristic rash. If you have recently been in contact with anyone who has chickenpox this can help to confirm your diagnosis.
Because chickenpox is highly contagious, it’s not advised that you visit your GP surgery, unless you have severe chickenpox or pneumonitis. It can easily be passed on to people who are at risk of complications. Either request a call with you GP or ask a pharmacist for advice.
However, if you have any doubt that it might not be chickenpox, or if you're pregnant or have a weakened immune system, see your GP.
There is no specific treatment for chickenpox and you will usually get better without any medicine.
You can take the following simple measures to help reduce your symptoms.
Chickenpox spots are usually very itchy, but try not to scratch them. Calamine lotion may help soothe and reduce the itchiness of your rash. You can buy this at a pharmacy. You can give your child paracetamol syrup (eg Calpol) to reduce fever and pain. Always read the patient information leaflet that comes with your medicine and if you have any questions, ask your pharmacist for advice.
You can also take an antihistamine, such as chlorphenamine, to help relieve any itching. These can be bought over the counter from a pharmacy. Antihistamines are taken by mouth and are suitable for children over the age of one.
If you develop serious complications of chickenpox, particularly pneumonitis or encephalitis, you may be given antiviral medicines to try to get rid of the virus more quickly. Aciclovir (Zovirax) is a medicine that helps you fight the varicella zoster virus. If you take it within a day of getting ill, your chickenpox will probably be milder. As a side-effect, aciclovir can sometimes cause diarrhoea and make you feel sick.
If you’re at risk of developing serious complications from chickenpox, you might be offered an injection that contains antibodies. These are proteins produced by your immune system that usually fight against bacteria and viruses. This helps fight your chickenpox. However, you need to have this within 10 days of coming into contact with someone who has chickenpox for it to work.
If you have chickenpox, try to stay away from people who haven’t had it. In particular, stay away from pregnant women, newborn babies and those with a weakened immune system. Because it’s hard to know who these people are, it’s best to try and stay away from busy public places. This is why it’s important not to visit your GP surgery if you can help it.
Keep your child off school or nursery for five days from the onset of the rash or until all the spots have crusted over. Air travel isn’t allowed until five days after the last spot has appeared.
There is a vaccine that can help prevent chickenpox, but it’s only recommended for certain people. For example, healthcare workers and for those in contact with someone with a weakened immune system. If you're thinking about getting pregnant and you have not had chickenpox, ask your GP about the vaccine. This is because catching chickenpox during your pregnancy could harm your unborn baby.
If you're pregnant and come into contact with someone who has chickenpox, there is no problem if you have had chickenpox before or have been vaccinated. If you have never had chickenpox or aren’t sure, see your midwife or GP as soon as possible. You can have a blood test to find out if you’re immune. If you develop any rash during pregnancy, always contact your midwife or GP.
If you aren’t immune to chickenpox and you come into contact with someone who has it during the first six months of pregnancy, there is a small risk it could affect your baby. You may be given an injection of varicella zoster immune globulin. This is a human blood product containing antibodies that strengthens your immune system for a short time. It doesn’t always prevent you from developing chickenpox but it can mean your symptoms are milder and don’t last as long if you do catch it.
You can have the injection up to 10 days after you come into contact with chickenpox and before any of your symptoms appear. Varicella zoster immune globulin doesn’t work once your spots have developed into blisters.
If you get chickenpox in the second half of your pregnancy, you may be given aciclovir. If you get chickenpox late in your pregnancy, especially around the time you give birth, your baby could develop chickenpox. See your GP if you get chickenpox within a week of giving birth. You and your baby can be treated with aciclovir or injections of antibodies.
It’s safe to breastfeed if you have or have had chickenpox during pregnancy. If you have chickenpox lesions very close to a nipple, you should express milk from the affected breast until the spots have crusted over. When your baby is seven months old, a blood test can check if he or she has antibodies to chickenpox. If your baby has these antibodies, it means that he or she has developed an immunity to the virus and is unlikely to catch it again.
If you catch chickenpox, you should stay away from other pregnant women and newborn babies until all your blisters have crusted over.
If you have a weakened immune system or you’re older than 65, you’re more likely to have serious complications as a result of catching chickenpox. If you come into contact with someone who has chickenpox and you haven’t had it before, speak to your GP straight away. The best way to prevent infection is to make sure that people you live with have the chickenpox vaccine, if they haven’t already had the virus.
Reviewed by Alice Rossiter, Bupa Health Information Team, November 2013.
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