Blog post: Do air purifiers, filters or humidifiers help asthma symptoms?

Dr Andy Whittamore looks at whether the latest technology can make a difference to your indoor environment

Author: Dr Andy Whittamore, Asthma UK’s in-house GP
Date: 18 July 2017

It’s understandable that adverts promising ‘clean, filtered, allergen-free air’ and ‘relief from respiratory symptoms’ are capturing people with asthma’s interest in air purifiers and filters. A few of my patients have asked me about them, and speaking to the nurses on the Asthma UK Helpline, they’re getting questions as well.

Do air purifiers and filters really work?

The truth is, more research is needed. Some people tell us having an air filter or air purifier helps them with their asthma symptoms. And most studies suggest they do improve symptoms if used alongside proven steps to manage asthma well.

So, if you’re considering getting an air purifier or filter, there are three things I recommend you do. First and foremost, keep on top of your asthma management. Then follow the tips below on finding the right device for you. And finally, monitor your asthma symptoms so you can see whether the air purifier is making a difference.

1. Take control of your asthma

This is crucial because the reality is air purifiers can’t remove all allergens and even a few left behind can trigger asthma symptoms. And, of course, you can’t take an air filter with you everywhere! That means you still need to be ready for everyday triggers - such as such as pollen, pollution and dust - if there’s a window open or when you go outside.

There are 3 simple ways of controlling your asthma:

2. Do your homework to get the right air filter or purifier device for you

Before you buy a device:

  • check what type of allergens it captures – will it get rid of your individual asthma triggers? 
  • check that the air purifier is ozone-free – some purifiers give out low levels of ozone which can make asthma symptoms worse
  • think about the noise level you’d be happy with as they vary
  • ask the company if they can offer you a trial period before you buy
  • clean and replace all filters when necessary.

Humidifiers, dehumidifiers and air ionisers

Some people with asthma tell us that humidifiers and dehumidifiers help with their asthma symptoms, but once again only if used alongside other methods. There isn't much research evidence about how effective they are.

Air ionisers are slightly different to air purifiers - they give out electrostatic charges to clean the air. However, there's no evidence that they improve asthma symptoms. Asthma UK doesn't recommend using an ioniser because some research shows that they increase night time cough in children.

3. Keep track of whether your asthma symptoms are improving

Asthma triggers vary from person to person, so what works for one person with asthma won’t necessarily work for someone else. And, because asthma symptoms also vary over the year - depending on the weather and people’s changing environment - it is important to work out whether it’s the air purifier that has made a difference or another factor.

To find out if the air filter is working for you, try keeping a symptom diary alongside your peak flow diary and note on there when you started using the device. Then you’ll be able to see if it has helped your asthma symptoms improve.

Even if your asthma symptoms have got better, it doesn’t necessarily mean that you can reduce or stop your asthma medication. Speak to your GP or asthma nurse at your next review if you have questions.


Dr Andy Whittamore is a GP based in Hampshire, specialising in respiratory care. He’s Asthma UK’s in-house GP, where he works on building relationships with key opinion leaders in respiratory care, identifying emerging issues in asthma, and providing the charity with clinical expertise.