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eMed previously Babylon Health


Written by Dr Claudia, 24th January 2019

This infectious disease of childhood, caused by the Varicella-zoster virus, is often seen as a milestone by many and frequently considered a mild illness that causes little more than a slight fever and frustratingly itchy child.

For otherwise healthy children, chickenpox includes a short period of feeling generally unwell, a typical all-over-body blistery rash, rapidly followed by a return back to their usual jolly and energetic selves.

Diagnosing chickenpox

Chickenpox presents with a very characteristic rash and most of the time this is all you need to diagnose chickenpox.

If you’re unsure whether your child’s rash is chickenpox or not – call your doctor and ask for advice, however remember not to visit a healthcare setting in person unless advised to by a doctor. This is because chickenpox is incredibly infectious and special precautions will need to be taken so that there is no risk of other patients coming into contact with your child.

Chickenpox is so incredibly infectious that 90% of people who come into contact with a person with chickenpox will also catch it, unless they’ve had it before.

When is someone infectious

This is the most common conundrum caused by chickenpox and is frequently confusing.

People are infectious (meaning they can spread the disease) from 1 to 2 days BEFORE the characteristic rash comes up. This means it is a good idea to inform those your child was in contact with the 2 days before being diagnosed with chickenpox.

People to inform include:

  • School/nursery/childcare provider
  • Anyone that might not have had chickenpox before (such as young babies)
  • Pregnant people (although only those that have not had chickenpox before are at risk)
  • Anyone that may be immunocompromised (undergoing chemotherapy for example)

How long is someone with chickenpox infectious for?

Usually 5 or 6 days, by which time all the spots will generally have crusted over.

Your child needs to stay off school/nursery for at least 5 days and until the spots have crusted over.

You also can’t fly until 5 days after the last spot appears. Make sure you check with the airline, as the length of time to wait after the infection starts can vary. The rash may hang around for some time and so usually you will need to get a letter from your doctor to take with you if you are travelling, in case anyone questions whether you are okay to fly or not.

How long after being in contact with chickenpox does the disease manifest?

The incubation period for chickenpox is between 10 and 21 days.

This means that if your child has come in contact with chickenpox, or if one of your children has chickenpox and there are others in the house that you are expecting to catch it – it will take up to 3 weeks for the rash to show.

As mentioned earlier, a person is only infectious for the 2 days before the rash appears, not for the whole 10 to 21 days in the run up.

Chickenpox in pregnancy

There is a lot of fear around contracting chickenpox in pregnancy. Here are the facts:

  • 90% of women will have had chickenpox at some point before becoming pregnant and so are immune and therefore their pregnancy won’t be affected.
  • For those women that are not immune and who contract chickenpox in pregnancy, there is a 10% risk of the mother becoming very unwell with it and 1-2% of the babies then born will have skin, eye, limb or neurological abnormalities.
  • It is worth noting that a) the risk of harm to the unborn baby is there up to 28 weeks of pregnancy, thereafter it seems the baby is not affected and b) there is no increased risk of miscarriage if the mum gets chickenpox in pregnancy.
  • Chickenpox can also be dangerous in pregnancy if the woman catches it from 7 days before the baby’s birth and onwards. This is because when the baby is born they can come in contact with the virus and so get infected with chickenpox.

If you are pregnant and at all concerned about this, speak to your GP. There is a blood test that can be done to check if you are immune or not to chickenpox. There is also treatment that we can give to mum and baby if needed.

When chickenpox becomes serious

Although chickenpox is generally a mild condition that rarely causes complications, it isn’t completely harmless either. Gone are the days where we would recommend “chickenpox parties”!

Common potential complications:

  • Scratching at the itchy spots can cause them to become infected
  • Scarring as a result of the spots which can be made worse by picking at them
  • Some children get spots in the mouth. This can be very painful and make eating so uncomfortable that they refuse to feed. This then puts them at risk of becoming dehydrated and very unwell. Do keep an eye out for this.

The more rare but serious complications include:

  • Infection of the brain (encephalitis) or the lining around the brain (meningitis)
  • Pneumonia

If your child gets chickenpox, be alert to any changes in behaviour/drowsiness/fits and any shortness of breath/coughing.

Managing chickenpox symptoms

The main problem with chickenpox is the itching. Some top tips to help manage the itching, besides the time and patience you will need in abundance, include:

  • Soothing baths (with oatmeal)
  • Antihistamines (such as Piriton)
  • Cooling gels and sprays (purchased over the counter on the advice of a pharmacist)

Avoid using the following:

  • Calamine lotion (as it sticks in the chickenpox spots and makes them even more itchy when it dries)
  • Aspirin (never give children aspirin, it is associated with a very unpleasant condition called Reye’s Syndrome)
  • Ibuprofen (a handful of studies have shown that in very rare circumstances giving Ibuprofen in chickenpox leads to a very serious life-threatening skin condition, so it is better avoided altogether unless recommended by your doctor)

The chickenpox vaccine

The chickenpox vaccine is currently not a part of the UK routine immunisation schedule. It can be purchased privately.

The information provided is for educational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Seek the advice of a doctor with any questions you may have regarding a medical condition. Never delay seeking or disregard professional medical advice because of something you have read here.