What are the main causes of asthma and asthma attacks?

GB-37400 DOP 04-2023

What causes asthma?

It may be common, but the exact causes of asthma are not fully understood. However, we do know that genetics and environmental factors can affect who develops the condition. We also know the common triggers that may cause symptoms to flare up.

In people with asthma, the smaller airways of the lungs (bronchioles) are sensitive to certain triggers which cause them to become inflamed. This makes the muscles around the airways squeeze and narrow (called bronchoconstriction), making it more difficult for air to get in and out of the lungs. Reliever inhalers act by relaxing these muscles - so-called bronchodilatation - opening up the airways.

This results in the common asthma systems - breathlessness, wheezing, and chest tightness. The lining of the airways is also triggered to produce extra mucus which further obstructs the airflow and can cause coughing.

Common risk factors

One person's asthma cause may be different to the next, but the World Health Organization (WHO) has identified these common risk factors:

• Having a close family member with asthma - such as a parent or sibling.

• Having other allergic conditions - such as eczema and hay fever.

• Living in an urban environment - multiple lifestyle factors can contribute.

• An event in early life affecting your developing lungs - includes a low birth weight, prematurity, exposure to tobacco smoke and other air pollutants, and viral respiratory infections.

• Being exposed to various environmental allergens and irritants.

• Being overweight or living with obesity.

What causes asthma attacks?

Not everyone who has asthma will experience severe asthma attacks - episodes of severe asthma symptoms. The causes are the same, but the difference is that the symptoms of an asthma attack are more debilitating than milder asthma symptoms.

You may be having a severe asthma attack if:

• Your chest tightness, wheezing or shortness of breath are becoming more severe and constant.

• You are too breathless to speak, eat, or sleep.

• You aren't getting relief of your symptoms from your reliever inhaler.

• You have a fast heartbeat.

• You feel confused, drowsy, dizzy, or exhausted.

• You have blue lips or fingers.

• You faint or feel as if you're going to black out.

What causes asthma in adults?

Asthma is often viewed as a childhood disease. According to Asthma + Lung UK around 1.1 million of the 5.4 million people being treated for asthma in the UK are under 16 years old - which is around 20% of all people diagnosed with asthma.

The percentage of people with adult-onset asthma (asthma that developed for the first time in adulthood) is significant.

Childhood asthma and adult-onset asthma share many of the same asthma causes and triggers. This said, research highlights that certain high-risk lifestyle factors play a key role in adult-onset asthma - for example, smoking, obesity (which can reduce the amount of natural bronchodilators in the body and increase inflammation), and occupation.

Occupational asthma may account for 9-15% of all adult-onset asthma cases. These are jobs which put people into greater contact with irritants and pollutants (such as gas, dust, and fumes) that can trigger asthma. Research finds that these tend to be lower-income manual jobs, making low socio-economic status another risk factor for asthma.

Asthma triggers and how to manage them

According to Allergy UK, an asthma trigger can be either allergic (due to allergen particles causing a reaction), environmental (to do with the quality of the air you breathe) or individual (related to your lifestyle).

Allergic asthma triggers

Margaret Kelman, specialist allergy nurse at Allergy UK, describes the common allergic asthma triggers:

• Pollen.

• House dust mites.

• Animals and pets.

• Mould.

Can hay fever cause asthma?

According to Kelman, hay fever can be both a cause of asthma in people who previously didn't have the condition, and an asthma trigger in those already living with it. Hay fever is a seasonal form of allergic rhinitis, where pollen (a fine powder produced by plants) enters the nose and causes an allergic reaction. More than 80% of people with asthma also have allergic rhinitis.

"It is vital that people with asthma and hay fever take their preventer inhaler as prescribed when pollen levels are high," cautions Emma Rubach, head of Health Advice at Asthma + Lung UK. "This reduces sensitivity and swelling in the airways, helping to prevent asthma symptoms before they even start. 

"We also advise people to carry their reliever inhaler (usually blue) when they are out and about enjoying the sunshine. Reliever inhalers relax the muscles in the airways quickly and ease symptoms on the spot."

Which indoor allergens can cause asthma?

For some asthma sufferers, it's not just outside that can pose a risk. Indoor allergens, such as mould, house dust mite, and pet allergy are also common asthma causes.

• House dust mites - microscopic creatures whose droppings can cause allergic reactions can be found in every house, regardless of how clean it is. However, areas that collect a lot of dust have a higher concentration, which is more likely to trigger asthma symptoms.

• Pets - sadly for many pet lovers, animal saliva, urine, and skin are the second most common cause of allergic reaction after house dust mite allergy. Cats and dogs are the pets most responsible for asthma flare-ups in our homes, due to the amount they lick their fur during grooming.

• Mould spores - a less common allergic reaction can occur when these miniscule particles are inhaled. These may even be brought into the house on your Christmas tree.

Environmental asthma triggers

The common environmental asthma triggers include:

• Weather changes.

• Pollution.

• Second-hand smoke.

• Indoor air quality.

How does the weather affect asthma?

• In the summer - those with hay fever usually experience more asthma flare-ups at this time of year - grass pollen season correlates with high consultation rates for asthma. High humidity can make this worse as it breaks pollen particles into smaller, more easily inhaled pieces. Spending more time outside also leads to greater exposure to smoke from barbecues, and air pollution.

• In the winter - Rubach says that exposure to cold, dry air can also exacerbate asthma. This may irritate the muscles that line your airways, making them spasm. In addition, common winter illnesses like flu, colds, and viruses can inflame the airways.

Individual asthma triggers

There are many other potential triggers you may be confronted with in daily life. Some are avoidable, while others aren't. The following factors have been found to act as triggers for many people with asthma:

• Your occupation.

• Smoking.

• Drinking alcohol.

• Exercising.

• Using perfume.

• Hormonal changes.

• Experiencing strong emotions - such as stress, anger, and laughter.

It's important to note that some factors - such as exercising and laughing - are essential for your health and well-being. Instead of avoiding these triggers, proper management of your asthma can allow you to better prevent or control symptom flare-ups.

Exercise advice

Getting your heart rate up through exercise bolsters your immune system and lung capacity, which can help control your asthma long-term.

1. Talking to your doctor or nurse and creating an asthma action plan can give you the confidence to exercise.

2. Research the best forms of exercise for asthma.

3. If exercise brings on your asthma symptoms, your doctor or nurse may advise you to take a dose of your reliever inhaler before you start exercising..

4. Follow Asthma + Lung UK's exercising with asthma safety tips.

Can smoking cause asthma?

"It is well known that smoking damages the lungs and can be a trigger for asthma attacks," says Rubach.

Tobacco is an irritant that can cause inflammation of the airways. Smoking can also damage cilia (tiny hairs) in the airways which allows mucus and dust to build up, making symptoms worse.

Can alcohol cause asthma symptoms?

"Occasionally, alcohol can trigger an asthma flare-up if you are sensitive to sulphites or histamine," Kelman advises. These compounds are found in certain alcoholic beverages, particularly in wine and beer. In one study of 366 people with asthma, wine was the most reported alcohol asthma trigger.

"Always have your reliever inhaler with you if you are planning on drinking. If you are sensitive to alcohol, it is best to avoid red wine, rosé, beer, and soda which all contain high levels of sulphites," cautions Rubach.

Can stress cause asthma?

Stresscan be a significant trigger of asthma attacks. What's more, prolonged stress in childhood has been linked with an increased risk of developing asthma.

In times of serious stress - such as during a panic attack - your body releases certain hormones that can make you breathless and increase your heart rate. This can put you at risk of asthma attacks or flare-ups.

Experts have also found that stress can damage your immune system response to illnesses and allergies and leave you more susceptible to other asthma triggers.

If stress is hindering your ability to manage your asthma effectively, Asthma + Lung UK recommend the following:

1. Adhere to an asthma routine - take your medicine, attend asthma reviews, and use a written asthma action plan.

2. Seek advice from your doctor or your asthma nurse.

3. Make healthy lifestyle changes to help reduce or manage stress.