Causes of asthma in children

There is no single known cause of asthma. However, certain things may increase the likelihood of your child developing asthma.

This can be due to your child’s genes or their environment, particularly in early life.

Increased risk

The likelihood of developing wheezing and asthma is increased if:

• there is a family history of asthma or other related allergic conditions (known as atopic conditions) such as eczema, hay fever or a food allergy 
• your child develops another atopic condition such as eczema, hay fever or a food allergy
• your child develops acute bronchiolitis (a lung infection, common in babies, that is caused by a virus )
• your child is exposed to tobacco smoke, particularly if the child’s mother smokes during pregnancy
• your child was born prematurely
• your child was born with a low birth weight (less than 2kg or 4.5lb)

Asthma triggers

Asthma can have a range of triggers, but they do not affect everyone in the same way. Once you know what your child’s asthma triggers are, you can try to avoid them.

Triggers include:

• Airway and chest infections – Upper respiratory infections, which affect the upper airways, are often caused by cold and flu viruses and are a common trigger of asthma. 
• Allergens – Pollen, dust mites, animal fur or feathers, for example, can all trigger asthma.
• Airborne irritants – Cigarette smoke, chemical fumes and atmospheric pollution may trigger asthma.
• Medicines – The class of painkillers called non-steroidal anti-inflammatory drugs (NSAIDs), including aspirin and ibuprofen, can trigger asthma for some people, although are fine for most. Children under 16 years of age should not be given aspirin. 
• Emotional factors – Asthma can be triggered by emotions, such as stress or laughing.
• Foods containing sulphites – Sulphites are naturally occurring substances found in some food and drink. They are also sometimes used as a food preservative. Food and drinks that are high in sulphites include concentrated fruit juice, jam, prawns and many processed or pre-cooked meals. Most children with asthma do not have this trigger, but some may.
• Weather conditions – A sudden change in temperature, cold air, windy days, poor air quality, and hot, humid days are all known triggers for asthma.
• Indoor conditions – Mould or damp, house dust mites and chemicals in carpets and flooring materials may trigger asthma.
• Exercise – Sometimes, people with asthma find their symptoms are worse when they exercise.
• Food allergies – Although uncommon, some people may have allergies to nuts or other food items, known as an anaphylactic reaction. If so, these can trigger severe asthma attacks.

Want to know more?

• Asthma UK: Asthma triggers A-Z.
• Causes of food allergies.  

What happens during an asthma attack?

During an asthma attack:

• the bands of muscles around the airways tighten
• there is increased inflammation in the linings of the airways and they become swollen
• the airways produce sticky mucus or phlegm, which can further narrow the airways

This narrows the passages of the airways, making it more difficult for air to pass through (in other words, making it more difficult to breathe). This can cause the characteristic wheezy noise. However, not everyone with asthma will wheeze. In a life-threatening attack, there may not be a wheezy sound.

An asthma attack can happen at any time. However, there are usually warning signs for a couple of days before, such as symptoms getting worse, especially during the night, and an increased need to use the reliever inhaler.

Asthma can sometimes be life threatening. See treating asthma in children for more information about how to manage your child’s asthma. Speak to your doctor or asthma nurse for further advice.

If your child or someone else is having a severe asthma attack and are unable to breathe, dial 999 immediately to request emergency medical treatment.

Want to know more?

• Asthma UK: Information for parents.