Many children will experience croup in their lifetime, and it is usually not a cause for concern given that it is generally not serious and does not last too long.¹ However, it is not widely known that there are two different types of croup.

While most children may suffer an episode of ‘viral croup’, children experiencing recurrent episodes may be diagnosed with another type of croup called ‘spasmodic croup’ (sometimes referred to as ‘recurrent croup’). If this is the case, there may be more to investigate with their condition. But before exploring this further, it’s important to understand what croup is. 

What is croup?

Croup (pronounced ‘croop’) is a common respiratory infection – an infection which affects the lungs, airways and other body parts involved in breathing. If you are not a parent or guardian of young children, you may not have heard of it before. This is because it largely only affects children under the age of 5, with most cases occurring in children between 6 months and 3 years old.¹

The spectrum of croup includes three respiratory infections called laryngotracheitis (lar-ingo-tray-kee-itis), laryngotracheobronchitis (lar-ingo-tray-kee-o-bron-kitis) and laryngotracheobronchopneumonitis  (lar-ingo-tray-kee-o-bronko-new-mon-itis). 

When you have these conditions, your white blood cells - whose function is to protect the body from disease – detect these foreign infections and rush to fight them off. This results in swelling of your larynx (voice box), trachea (windpipe) and large bronchi (airways), which in turn causes other symptoms which will be explored further in this article – such as difficulty breathing.²

Fortunately, croup is often not serious and very few cases result in hospitalisation.³ It is a self-limiting disease, which means that it usually goes away on its own after a certain period of time.⁴  However, a doctor may begin to suspect spasmodic croup if a child keeps experiencing recurrent episodes. So, what is the difference between viral and spasmodic croup? 

Viral croup vs spasmodic croup 

Causes – viral croup

As the name would suggest, most cases of viral croup are caused by a virus – it enters the body and starts to attack the upper parts of the breathing system, which then causes swelling in these aforementioned areas (Harvard Medical School). The most common viruses to cause viral croup are Human Parainfluenza Viruses which are detected in up to 80% of patients. The human parainfluenza virus has different types, and type 1 has been found to be the most common among these patients, meaning that type 1 parainfluenza is a common cause of viral croup.⁵

Some other viruses which have been found to cause viral croup include:

• Enterovirus
• Human Bocavirus – a recently identified pathogen that causes respiratory illness in children
• Influenza A and B viruses – “the flu”
• Respiratory Syncytial Virus (RSV) – a common virus that causes coughs/colds
• Rhinovirus – a “common cold”
• Adenovirus 
• Measles   

Most cases of croup occur in the winter because a lot of these viruses are more prevalent at this time of year – potentially because people spend more time inside in close proximity to each other. Viruses like these can spread when you breathe in droplets of the virus in the air (released when someone coughs or sneezes), or when you touch a surface that the virus has been transmitted to (by somebody who is infected touching it before you). ⁶ This means that viral croup can spread very easily among young children who tend to share toys and put their fingers in their mouths a lot. 

Although it is very rare, there have also been cases where croup has been caused by bacteria rather than viruses. Examples include diphtheria (which is rare in the UK) and mycoplasma pneumonia.

Causes – spasmodic croup

While it is well known that an episode of viral croup is caused by an infection when a child continues experiencing recurrent episodes of croup and is subsequently diagnosed with spasmodic croup, the causes of this are much less clear. Unlike viral croup, spasmodic croup can occur in a child who presents with no symptoms of infection. When this is the case and an infection does not appear to be the cause, there could be other reasons behind the onset of the croup, such as:

• An abnormality in the child’s airway which could be causing an obstruction 
• GORD (gastro-oesophageal reflux disease) – heartburn and acid reflux 
• Asthma or another similar airway disease 
• Allergies
• Eosinophilic oesophagitis (EoE) – a condition involving inflammation of the gullet 

These are some selected examples of what could be causing spasmodic croup. In essence, it is thought that rather than being seen as a different disease itself, spasmodic croup should be seen as a symptom of another underlying problem– such as those listed above.⁷ The key difference in terms of causes between the two types of croup, therefore, is that things like allergies and asthma are thought to be significant causes of spasmodic croup, rather than viruses. 

Symptoms – both types of croup

The swelling of the windpipe, voicebox and airways in viral and spasmodic croup can cause these common symptoms:

• A barking cough which can sound like a seal 
• Raspy, laboured breathing 
• A high-pitched, harsh, whistling sound when breathing in called a stridor

These symptoms are nearly always worse at nighttime. It is not known exactly why, but this may be linked to our hormone levels which change as part of our body’s circadian rhythm (our internal clock telling us when to be alert or sleepy).⁸

Symptoms – viral croup

Children with viral croup may also present with symptoms such as: 

• Fever (usually low-grade)
• Runny nose & other cold-like symptoms

These cold-like symptoms usually precede the cough and last for a few days.

Symptoms – spasmodic croup

However, children with spasmodic croup often appear healthy until they begin coughing, and do not normally have a fever. This can mean that the episodes of coughing and raspy breathing can come on very abruptly without warning, usually in the middle of the night. Unlike viral croup, these symptoms seem to then improve within a few hours, but they often return several nights in a row (Harvard Medical School).

Treatment for croup 

As a self-limiting disease, croup will usually go away on its own within a couple of days. To alleviate symptoms in your child, the NHS recommends that you:
Try to keep your child sitting upright:

• Give them lots of fluids. 
• Check on them frequently. 
• Help to bring down their fever with paracetamol or ibuprofen 
• Comfort them if they are crying, as crying can make symptoms worse

If a child requires medical treatment for their croup, they will often be given a type of steroid called dexamethasone to resolve their symptoms. In more severe cases, they may also be treated with other nebulised medications (a liquid drug turned into a spray) or oxygen. Cough medicines are not advised as they usually contain certain ingredients which are not suitable for treating croup – nor is steaming, due to lack of evidence that it works. In the very rare event that croup is caused by a bacteria, antibiotics may be used.¹

When should I seek medical attention for my child? 

If you believe your child is suffering from croup, it is a good idea to consult a doctor (particularly if the illness has lasted more than 3-5 days), as they may be able to help speed up recovery.

You should seek emergency treatment if your child: 

• Is struggling to breathe (listen for different breathing noises or grunting sounds)
• Is having trouble swallowing or is drooling 
• Is unusually quiet or sedentary 
• Is hard to wake up or is sleeping more than usual 
• Can’t be calmed down 
• Is limp and floppy 
• Has blue/grey/pale/blotchy tongue, lips and/or skin 
• Has a fever above 39°C

How can I prevent my child from getting croup? 

Whilst it is hard to prevent croup spreading given how contagious it is amongst children, there are things you can do to help. As it is caused by viruses, the best thing you can do is fight the spread of germs by:

• Encouraging your child to wash their hands frequently and properly 
• Keeping them away from people who have respiratory infections like the flu or a cold, where possible 
• Teaching them to sneeze and cough into a tissue 
• Regularly cleaning the surfaces they touch 

Summary

As a very common, contagious condition, most children will likely experience an episode (or two) of croup. However, the key takeaways to remember are: 

• It only tends to occur in children under the age of 5
• The vast majority of cases are mild and will heal on their own in time 
• Viral croup is caused by an infection (most often, viruses)
• Spasmodic croup is when an episode of croup is recurrent, and is likely caused by allergies or asthma rather than viruses
• Children with croup may have a barking cough, hoarse voice, stridor or difficulty breathing due to swelling in their breathing system
• Staying upright, hydrating, remaining calm and taking paracetamol or ibuprofen can help with symptoms
• If medical attention is needed, they may be treated with a type of steroid 
• If symptoms become severe, emergency treatment should be sought 
• Washing hands, keeping away from people with colds/flu and cleaning surfaces can help stop the spread of viruses that cause croup