A selection of asthma triggers

Understanding asthma triggers

Knowing what your asthma triggers are, and how to manage them, can lower your risk of symptoms

Health advice > asthma triggers

Find out what an asthma trigger is, how to find out your triggers, and how to lower your risk of asthma symptoms.

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What is an asthma trigger?

An asthma trigger is anything that can set off your asthma symptoms. Triggers can make your airways more inflamed and can cause asthma attacks. A few things happen when you come into contact with a trigger:

  • Muscles around the airways tighten.
  • The lining of the airways become swollen and inflamed.
  • Sticky mucus can build up in the airways.

This is what causes your asthma symptoms, such as coughing, breathlessness, chest tightness or wheezing.

Triggers can change over time, and some will depend on the time of year, or the environment you’re in. Cold air can affect people in winter, and pollen can affect people in spring and summer.

Other common triggers include:


You might have one or two triggers, or you may have several. Everyone with asthma has their own set of asthma triggers, and what sets off your symptoms, might not set off someone else’s. It’s important to know what your triggers are so that you can avoid them if possible.

How can I tell what triggers my asthma?

Sometimes it’s obvious what your triggers are. For example, your symptoms may come on quickly after coming into contact with a cat or dog, or when you’re around people who are smoking.

But it can sometimes be harder to know what’s causing your symptoms. Some triggers aren’t as obvious if they’re not visible, for example pollen or indoor air pollution. And sometimes your reaction might be delayed, or it might build up over a few days.

It might help you to keep a diary of activities and symptoms, or keep a record of your peak flow, to help you spot patterns.

Why are my reactions to triggers sometimes different?

Your reactions to triggers may not always be the same. If your airways have been inflamed for a long time, they become more sensitive – and sensitive airways react more to triggers.

You may find your airways are more sensitive when you come into contact with multiple triggers too.

“Your triggers and the inflammation in your airways can come and go and can be hard to predict. The best way to help stop these causing symptoms making you unwell is to reduce the inflammation by taking your preventer inhaler every day, as prescribed,” says in-house GP, Dr Andrew Whittamore.

How to deal with asthma triggers

Avoiding your triggers

Write down the triggers you notice on your asthma action plan. Once you’ve worked out what triggers your asthma, you can start to avoid them if possible. It may also be a good idea to tell your friends and family what your triggers are, so they can help you to avoid them.

Common triggers such as cigarette smoke can be avoided by making sure nobody smokes inside your home and other places that you spend time.

Managing your asthma well

There are steps you can take to cut your risk of asthma triggers causing symptoms or an asthma attack:

  • Take your preventer medicine as prescribed – this keeps inflammation down in your airways so you’re less likely to react badly to triggers.
  • Use an asthma action plan to note down your triggers.
  • Go to your annual asthma reviews to make sure your treatment plan is giving you the best protection against your triggers and cutting your risk of an asthma attack. You can also check your inhaler technique.

It’s important to always keep your reliever inhaler with you. This will help you deal with symptoms quickly as soon as they come on.

Find out more about managing your asthma well.

You can call our Helpline on 0300 222 5800 (9am - 5pm; Mon - Fri) to talk to a respiratory nurse specialist about understanding your asthma triggers. Or you can WhatsApp them on 07378 606 728.


Last updated January 2022

Next review due January 2025

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