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Uncommon childhood illnesses you should know about

WebMD Feature
Medically Reviewed by Dr Rob Hicks

Part of being a parent usually involves wiping clean a toddler's running nose when they have a cold and comforting a child as they recover from vomiting or diarrhoea. Treating these common childhood illnesses often becomes second nature among parents – but there are other childhood illnesses that we may be less aware of.

Illnesses that you may not know about

There is a list of infectious diseases that many parents have vaguely heard of. What exactly is croup, and isn't scarlet fever a thing of the past? Ask a group of parents "What is bronchiolitis?" or "What is slapped cheek disease?" and they may tell you they’ve never heard of them – yet these are relatively common illnesses.

Before your child develops an unusual cough or strange rash, read about these less familiar childhood illnesses to prepare yourself for the unexpected.


The respiratory syncytial virus (RSV) is usually the culprit responsible for bronchiolitis, a type of respiratory infection that affects the lungs, usually during the winter. About half of children in the UK will have had an episode of bronchiolitis by the time they reach 2 years old and almost all 2 year olds will have been infected by RSV. The RSV infection often causes a cold or cough in older children and adults, but in young children it can affect the lungs causing bronchiolitis.

The virus spreads by tiny droplets that are released by sneezing or coughing and in young children it can make its way into the bronchioles – tiny airways inside the lungs. The infection causes mucus to develop, and the mucus and swelling in the bronchioles can make it difficult to breathe. Bronchiolitis is normally mild and gets better without treatment within 2 weeks, but 3% of babies under a year old in the UK will be admitted to hospital each year. If you are worried about your baby or child, seek medical advice. If your baby or child is having difficulty breathing, seems pale or sweaty, has a blue tongue or lips or there are long pauses in breathing, dial 999 for an ambulance.

Dr Penny Woods, chief executive of the British Lung Foundation, says: "While in most instances bronchiolitis is not serious, parents would do well to look out for those crucial signs that might identify a more severe case in their child."

Though bronchiolitis is a very infectious disease, Dr Woods explains it is also largely preventable. She says, "Simple steps like washing hands and wiping down toys to prevent the spreading of germs can make all the difference in protecting children's lungs."


A cough that has a distinctive barking sound is the most noticeable symptom of croup, an illness in which the windpipe, the voice box and the airways to the lungs are affected by a virus. Other symptoms include stridor – a harsh sound made as the child breathes in – and possibly a hoarse voice and struggling to breathe.

About 3% of children get croup every year. Although croup sometimes occurs in babies as young as 3 months old and in older children up to 15 years old, children between 6 months and 3 years old are more likely to get croup, with one-year olds accounting for most cases. Outbreaks typically occur during the winter months. Croup is usually mild enough to be treated at home and usually clears up within 2 days, but if your child is struggling to breathe seek medical advice. A steroid medicine may be recommended to ease symptoms but some cases may require hospitalisation.

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