Common asthma triggers


A number of factors can trigger, aggravate or worsen your asthma.

Below is a checklist of asthma trigger factors. Once you’ve identified the trigger factors that affect your asthma, you should work on avoiding them. If you can’t determine what triggers your asthma, talk to your doctor.

1. Allergies
An allergic reaction is the most common cause of asthma. Here is what happens during an allergic reaction:

  • The allergen (e.g. pollen, cat dander) causes the lining of the airways (bronchi) in your lungs to become more inflamed and swollen. It also causes the muscles in the walls of your airways to narrow and breathing becomes difficult.

See our article on asthma prevention to learn more about controlling your allergies.

2. Colds, flu and co-existing conditions
A cold and the flu can aggravate your asthma symptoms temporarily. The worsened asthma symptoms may last for up to six weeks after the start of the flu or cold. In fact, many asthma attacks are caused by the common cold.

It’s very important to get good asthma therapy to prevent asthma attacks during and/or after suffering from a cold or the flu. This cannot be overemphasised. Also remember that both the common cold and the flu are caused by viruses and that antibiotics won’t work and shouldn’t be used. Antibiotics only work if you have a bacterial infection like pneumonia or bronchitis.

Consider getting your annual flu vaccine in March/April every year. Ask your doctor about getting a flu shot if:

  • You’ve been hospitalised as a result of asthma in the past year.
  • You recently had to increase your inhaler dose.
  • You’ve been diagnosed with severe asthma.
  • You’re pregnant, older than 65 or obese.
  • You have another chronic health condition (e.g. heart disease or diabetes).

3. Pollution
Once you have asthma, home and workplace chemicals (e.g. bleach), tobacco smoke, car exhaust fumes, and certain chemical gases can aggravate your condition. It’s best to stop smoking and to avoid all smoking areas – passively inhaling cigarette smoke may trigger an attack.

New carpeting and furnishings often release formaldehyde, a common asthma trigger. If your home or office is being redecorated, increase ventilation by opening windows and doors.

4. Sport and exercise
Sport and exercise, particularly in cold weather, can set off an asthma attack. But with the correct treatment, asthma can be controlled to such an extent that you don’t have to avoid exercise. In fact, about 10% of Olympic athletes have asthma, yet they’re able to excel at their respective disciplines.

5. Emotions
Emotions such as excitement, anger, fear, crying or laughter can change your breathing and bring on an asthma attack.

6. Medicines
Certain commonly used medicines, such as aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs), may trigger a severe, even fatal asthma attack. If you have a known sensitivity to these drugs, you have to steer clear of them completely.

Also be cautious when using ‘beta blocker’ blood-pressure medicines or eye-drops for glaucoma, as they may constrict the airways.

7. Other conditions
Conditions that may trigger asthma attacks include:

  • Infection of the sinuses (sinusitis).
  • Soft, round, mucous-producing tissues that project into the nasal passages (nasal polyps).
  • Reflux (back flow) of stomach contents into the oesophagus (gastro-oesophageal reflux disease).

To summarise, here is a list of common asthma triggers. Tick whether any of the following apply to you:

Asthma triggers

Tick, if applicable

Exercise / sports / activity


Animals (dogs, cats, feathers)


Foods (nuts, eggs, fish, shellfish, milk products, food additives and preservatives, wheat) 


House dust mites


Viruses (colds, flu), sinusitis, chest infections


Irritants and pollutants, e.g. smoke, care exhaust fumes, strong smells (paint, glue), cleaning chemicals, air fresheners


Pollen and grass


Changes in weather, e.g. cold weather, rain, wind


Work environment, e.g. fumes


Medicines (aspirin, other non-steroidal anti-inflammatory medicines, beta blockers)


Perfumes, deodorants, hair spray


Cockroaches, rodents


Indoor mould, fungal spores, mildew


Strong emotions, e.g. excitement, anger, fear, laughter


Gastro-oesophageal reflux


It’s best to develop an action list for each of the triggers you’ve identified. Have a look at the examples below and remember: it’s easier to prevent your asthma from occurring than to treat it.



Animal dander

  • Don’t keep a family pet or make sure the animal stays out of your bedroom. 
  • Seal or cover air ducts leading to the bedroom.
  • Fit air filters.

House dust mites

  • Cover your mattress and pillows with an impermeable cover.
  • Wash bedding once a week in boiling water.
  • Reduce indoor humidity to less than 50%.
  • Remove carpets.
  • Opt for wooden rather than upholstered furniture.


  • Keep a clean house. Don’t leave out any crumbs and other morsels of food.

Exercise / sports / activity

  • Using two puffs of your reliever therapy 15 minutes before exercise will keep your asthma symptoms at bay for 1-2 hours.


  • Take note of what you ate before an asthma attack and make a note of the preservatives in the food. Keep tabs on whether you get another attack if you eat the same food again. If so, avoid the food.


  • Get your annual flu shot in March / April.
  • Avoid contact with people who have a cold or the flu.
  • Wash your hands after contact with someone who has a cold or the flu.
  • Consider stepping up your asthma treatment – speak to your doctor.

Cold weather

  • Dress warmly before going outside.
  • Keep a gown close to your bed.
  • Always take a jacket or jersey to the office (the air conditioning may be very cold).

Smoke, pollen, perfumes

  • Avoid contact with these common asthma triggers.

Reviewed by independent healthcare consultant Prof Praneet Valodia and pulmonologist Prof Elvis Irusen, Head of the Division of Pulmonology at the Faculty of Medicine and Health Sciences, Stellenbosch University. October 2018.

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