A selection of asthma triggers

Understanding asthma triggers

Knowing what your triggers are and how to deal with them means you’re more likely to stay well with your asthma.

That’s why it’s so important to take your preventer inhaler every day. It keeps down the inflammation in your airways, so you’ll be less likely to react to your asthma triggers. 

What’s an asthma trigger?

An asthma trigger is anything that can set off your asthma symptoms. Common triggers include colds and viruses, pets, cigarette smoke, cold weather and pollen.

You may have just one or two triggers, or several. What sets off your asthma symptoms may be different to what sets off someone else’s. Everyone with asthma has their own set of asthma triggers.

It’s helpful to know what your triggers are so you can avoid them if possible.

How do you know what your asthma triggers are?

Sometimes it’s obvious what your triggers are, for example, when your symptoms start after coming into contact with a cat or dog, or when you’re around people smoking.

But it can sometimes be harder to pinpoint what’s causing your symptoms, perhaps because it’s a trigger like grass pollen, or dust mites, which you can’t see. Or because your reaction is delayed or builds up over a few days.

A bit of extra detective work may be needed – try keeping a diary of activities and symptoms to help you spot any patterns.

Why is a reaction to a trigger sometimes worse than at other times? 

Sometimes you may be more likely to react badly to your usual asthma triggers than at other times. This may be because asthma symptoms are caused by more than one asthma trigger at the same time. For example, if you have a cold and you also come into contact with a cat it can cause a stronger reaction. 

“The sensitivity in your airways can vary day to day, month to month and year to year,” says Asthma + Lung UK nurse, Kathy. “But to keep things steady, and stay on top of the inflammation, take your preventer inhaler every day as prescribed. That way your triggers are less likely to cause symptoms.”

How to deal with asthma triggers

Some asthma triggers are avoidable, such as cigarette smoke, pets and alcohol. But it’s impossible to completely avoid others – things like pollen, pollution, and cold weather.

The good news is there are proven steps you can take to cut your risk of asthma triggers causing asthma symptoms or an asthma attack. 

We hope you have found this content useful

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The best way to help your body cope well with any asthma triggers is to take your preventer inhaler every day as prescribed.

Your preventer medicine works away in the background to help inflammation and sensitivity in your airways.

Taking it every day, and in the right way, means there’s less chance of a reaction if you come into contact with any triggers. 


Use your written asthma action plan to note down your triggers so you can spot when your asthma needs extra help.


Using an action plan helps you manage your symptoms so you're less likely to end up in hospital for your asthma. 

If you haven’t got one, download an asthma action plan now and fill it in with your GP or asthma nurse.


An asthma review gives you and your GP or asthma nurse a chance to make sure your written asthma action plan is up to date.

You can check you’re taking the right medicines at the right doses so you’re getting the best protection against your triggers and cutting your risk of an asthma attack.

You can also check you’re using your inhaler in the best way - it might be that something as simple as a change of inhaler technique could help you manage your asthma better.


Last updated January 2019

Next review due January 2022