A trigger is anything that irritates the airways and causes the symptoms of asthma, including psychological pressures such as stress. Asthma affects people differently and there may be several or many triggers. An important part of controlling asthma is avoiding triggers. Common triggers include:
  • house dust mites
  • pets
  • animal fur
  • animal saliva
  • feathers
  • perfume
  • mould or fungi
  • pollen
  • pollution or poor air quality
  • tobacco smoke
  • exercise
  • cold air and humid air
  • viral infections
Asthma and allergies
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Asthma is closely related to allergies; people with hay fever, eczema or other allergies are more likely to develop asthma. Contact with allergens can be one of the triggers for breathlessness and uncontrollable coughing, but not everyone who has asthma will have allergic asthma. The most common form of asthma is known as ‘Atopic’ asthma – so called because the person has ‘atopy’ which is a tendency to allergic reactions. Asthma that is not allergy related may be triggered by stress, exercise, cold air or viruses. People can experience one or both types of asthma.
It can be difficult to identify exactly what triggers asthma and even if identified triggers can be hard to avoid, but if they can be found unnecessary symptoms can be reduced and the asthma better controlled. Sometimes the link is obvious, for example when symptoms start within minutes of contact with a cat or dog. But a delayed reaction to an asthma trigger can make it difficult to work out. Some people mentioned various things that could make their asthma flare up.
The weather was often a key trigger, particularly the change to colder and damp weather. Some people get asthma only in winter and may have no symptoms at other times of the year; for others the summer is worse, especially if grass and pollen are among their triggers. Alice’s breathing becomes much more difficult when the air is cold and even briefly opening the back door in cold weather can set off her asthma.
Some people find that their asthma flares up during summer or when the weather is humid. Humid weather triggers Ann’s asthma and she is now sensitive to some plants - her love of gardening has had to take a back seat since she had asthma. "I seem to be affected by temperature changes, by weather changes. So I'm badly affected when the weather is very cold, when it's very wet, when it's very hot. I'm affected … when I get hay fever symptoms."

People with asthma also may get hay fever during summer when the pollen count is high. Even hanging out washing in the garden in summer would make them feel wheezy and breathless. Some people may also find it helpful to take antihistamines (particularly if their asthma is allergy based) which provide quick relief for symptoms such as sneezing, runny nose, itchy, watery eyes and itchy throats. Mark also gets hay fever-triggered asthma and finds it difficult to tolerate being outside in summer, especially as he lives close to fields where rapeseed grows.
Viral infections are a very common trigger. During the winter months, people may find it difficult to shake off coughs, colds and chest infections, which may worsen their asthma symptoms. To most people getting a cold is a normal part of life, but a cold or chest infection can make Jenny, who has severe brittle asthma, quite ill, sometimes landing her in hospital.
Because colds and flu are triggers for many people with asthma and their asthma can get much worse, people with asthma are usually offered the flu vaccine as a preventative measure. This can be highly effective for most people, although one person we interviewed was allergic to it.
Allergy to various things is a common trigger for some people. As well as pollen, people often mentioned dust and house dust mites, and animal fur or feathers (including their own pets). Jan’s asthma was diagnosed when she was 4; her parents have told her that the first attack was triggered by contact with a pet rabbit. Mark had difficulty near pollen or animals as a child.
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Catherine has certain friends who she can’t visit because she is allergic to their pets, but they understand and make arrangements to visit her at her own home. Although most people said their friends wanted to help, some said that occasionally they had met people who had been insensitive towards them. Catherine had one friend who had a cat but would refuse to put the cat out of the room or hoover up when Catherine visited. And I kept trying to say to her, you know, “This is why I’m sneezing, coughing, wheezing, taking my inhaler constantly, because of the cat” but even though I tried to tell her the impact for some reason some people just don’t take you seriously.”

Pollution, especially from traffic, is increasingly recognised as making asthma worse. Alice and Jane both said that traffic fumes and waiting in train stations could set off their asthma. Chemical irritants such as cleaning products, shoe polish, nail varnish and perfume can be triggers for some people. Often people talked about how they avoided using certain cleaning products and how they had adapted their house to keep it as dust-free as possible. Reducing exposure to house dust mites is recommended in the British Thoracic Society guidelines, although evidence from trials has so far shown little effect on asthma symptoms.

Smoking or being exposed to a smoky atmosphere can irritate the lungs and bring on asthma symptoms. Exposure to tobacco smoke in childhood, or if your mother smoked during pregnancy may increase your likelihood of getting asthma. Belinda’s parents both smoked at home in the 1960s when she was a child; she thinks passive smoking contributed to her asthma. When Gail stopped smoking her symptoms disappeared almost completely. Esther used to smoke when she was younger but is now very sensitive to being in a smoky atmosphere. Some people said that the smoking ban in public places has enabled them to go out and socialise more.
Some people can get asthma through exposure to irritants at work. This is known as Occupational Asthma.

In some people certain foods can trigger asthma. People talked about a variety of things that could set off their asthma including dairy products, fizzy drinks, certain wines and beers. Charles said that white wine in particular can make him feel wheezy. Even a small amount of alcohol such as in sherry trifle can make Jenny’s asthma flare up.
Many people’s asthma flared up during or after exercise. Exercise can make people breathless, but there is a difference between ordinary breathlessness, and that associated with asthma. Some people get wheezy and unable to breathe properly if they over-exert themselves and it is quite understandable that they avoided exercise as a result. However, exercise-induced asthma can usually be controlled and several people told us that they could do exercise as long as they used their reliever inhaler beforehand, or they might stop for a short while to have a puff of the reliever. People who exercised regularly felt the benefits and found their lung function improved.

Asthma can be triggered by stress or emotion. Some people’s asthma got worse when they felt anxious or stressed. Christine’s first asthma attack came in childhood when her mother was seriously ill and she was very anxious. Several people said that it could be difficult to control stress levels in the midst of an asthma attack. People spoke of a ‘vicious circle’ because the more stressed you become, the harder it is to control.
Sometimes women found that the onset of symptoms had coincided with the timing of their menstrual periods.
Many people have a range of triggers, which may change over time, either when existing triggers become less of a problem or something new can start up. Sometimes people told us specifically about things that caused them no trouble, even though they may be a problem for others with asthma.
Tim, for example, is fine with dogs, and some cats, but cannot visit one friend who has several cats. Jenny has her own dog. Belinda has trouble with smoky atmospheres but not with dust, traffic or animals.
Sometimes it can be difficult to know just what triggers someone’s asthma. Margaret is still puzzled and says even after lots of allergy tests she’s none the wiser about what it is that makes her asthmatic. "I’ve had all the pinpricks on your arm for allergies. And I think they chose the four main triggers and I didn’t test positive for any of them. Cats, dogs, grasses or any of that. Just didn’t. It’s one of those unexplained things". Jane discovered by chance that her asthma was triggered by changing hormone levels in the body, from the time when she was a teenager, and more recently during the menopause.

(Also see ‘Asthma in the workplace’, ‘Exercise, diet, weight and other lifestyle issues’, ‘Managing asthma – reviews and action plans’ and ‘Finding information about asthma’).


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