Humidifiers & ionisers

Humidifiers and ionisers work in different ways but can help make the air better for asthma sufferers and therefore help reduce the symptoms that may bring on an asthma attack.


Humidifiers will raise the humidity of a room by adding moisture to the air and therefore children and adults with asthma will often find that a humidifier will help their breathing since it eliminates the dry air that can irritate and inflame the passages in the nose and throat.

Indoor humidity levels should remain between 30 and 50%. If the humidity level drops below 30% people can suffer from dry mucus membranes which can lead to or aggravate the symptoms of asthma. Levels can be monitored with a device called a hygrometer, and many humidifiers will have these built in. Humidifiers tend to be more beneficial during the winter, when humidity levels are low and heating systems are in use since they dry the air out.

It is recommended that asthma sufferers use filter humidifiers that use a HEPA filter. These units will remove harmful toxins and allergens from the air and do not produce ozone. There are two types of humidifier:

  • Hot mist – these contain a heating element that boils water and then puts moisture into the air by sending out a stream of hot mist.
  • Cool mist – these force the water droplets into a mist by a mechanical action and then disperse the mist into the air. Cool mist is generally easier to breathe.

Any humidifier will need to be drained and cleaned frequently since bacteria can multiply in dirty and stale water. If the humidifier is being used for a child it is better to use a cool mist humidifier to avoid accidental steam burns.

It is important not to keep humidity levels too high since this can make things worse by prompting the growth of mold or mildew.


Negative ions are produced in nature and found in mountain tops, near waterfalls, oceans and after a thunderstorm shower. Ionisers re-create this environment, cleaning the air by releasing billions of negatively-charged ions that ‘wrap’ themselves around positive ions and draw them back into the ioniser.

Ionisers can therefore provide fresher and cleaner air in the home or car and more importantly for asthma sufferers also remove dust particles, smoke, pollen, skin cells, pet hairs, fungal spores and smells from the air which can help relieve their asthma symptoms.

Information contained in this Articles page has been written by talkhealth based on available medical evidence. Our evidence-based articles are certified by the Information Standard and our sources are available on request. The content is not, though, written by medical professionals and should never be considered a substitute for medical advice. You should always seek medical advice before changing your treatment routine. talkhealth does not endorse any specific products, brands, or treatments.

Information written by the talkhealth team

Last revised: 6 December 2012

Next review: 13 December 2014