A trigger is anything that irritates the airways and causes the symptoms of asthma.
Everyone’s asthma is different and you will probably have more than one trigger.
Common triggers include colds or flu, tobacco smoke, exercise and allergies to things like pollen, furry or feathery animals or house-dust mites.
These videos about asthma and living with it were made by Asthma UK.
For more information on asthma, visit asthma.org.uk