Asthma Management Handbook

Assessing asthma triggers


Assess each patient’s asthma triggers to identify those that are clinically relevant to the individual and whether they are potentially avoidable.

Table. Summary of asthma triggers Opens in a new window Please view and print this figure separately:

How this recommendation was developed


Based on clinical experience and expert opinion (informed by evidence, where available).

List important triggers on the person’s written asthma action plan.

How this recommendation was developed


Based on clinical experience and expert opinion (informed by evidence, where available).

More information

Interactions between triggers

Simultaneous exposure to some classes of triggers may have synergistic effects on asthma symptoms and flare-ups, e.g.:

  • allergens plus industrial or traffic pollutants (e.g. diesel exhaust, ozone)12
  • allergens plus viruses.34
Thunderstorm asthma

Certain types of thunderstorms in spring or early summer in regions with high grass pollen concentrations in the air can cause life-threatening allergic asthma flare-ups in individuals sensitised to rye grass, even if they have not had asthma before.5, 6, 7, 8, 9

Sensitisation to rye grass allergen is almost universal in patients who have reported flare-ups consistent with thunderstorm asthma in Australia.

People with allergic rhinitis and allergy to ryegrass pollen (i.e. most people with springtime allergic rhinitis symptoms) are at risk of thunderstorm asthma if they live in, or are travelling to, a region with seasonal high grass pollen levels – even if they have never had asthma symptoms before. This includes people with undiagnosed asthma, no previous asthma, known asthma.56 Lack of inhaled corticosteroid preventer treatment has been identified as a risk factor.5

Epidemics of thunderstorm asthma can occur when such a storm travels across a region and triggers asthma in many susceptible individuals. Epidemic thunderstorm asthma events are uncommon, but when they occur can they make a high demand on ambulance and health services.10911

Data from thunderstorm asthma epidemics suggest that the risk of asthma flare-ups being triggered by a thunderstorm is highest in adults who are sensitised to grass pollen and have seasonal allergic rhinitis (with or without known asthma).5

The worst outcomes are seen in people with poorly controlled asthma.10 Treatment with an inhaled corticosteroid asthma preventer was significantly protective in a well-conducted Australian case-control study.6

There is insufficient evidence to determine whether intranasal corticosteroids help protect against thunderstorm asthma. Intranasal corticosteroids reduce symptoms of allergic rhinitis and limited indirect evidence suggests they may protect against asthma flare-ups in people not taking inhaled corticosteroids.12

The effectiveness of specific allergen immunotherapy in protecting against thunderstorm asthma has not been evaluated in randomised clinical trials, but data from a small Australian open-label study suggest that short-term treatment with five-grass sublingual immunotherapy may have been protective in individuals.13

Last reviewed version 2.0



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  2. Dales RE, Cakmak S, Judek S, et al. Influence of outdoor aeroallergens on hospitalization for asthma in Canada. J Allergy Clin Immunol. 2004; 113: 303-6. Available from:
  3. Green RM, Custovic A, Sanderson G, et al. Synergism between allergens and viruses and risk of hospital admission with asthma: case-control study. BMJ. 2002; 324: 763. Available from:
  4. Murray CS, Poletti G, Kebadze T, et al. Study of modifiable risk factors for asthma exacerbations: virus infection and allergen exposure increase the risk of asthma hospital admissions in children. Thorax. 2006; 61: 376-82. Available from:
  5. Davies J, Queensland University of Technology. Literature review on thunderstorm asthma and its implications for public health advice. Final report. Melbourne: Victorian State Government Department of Health and Human Services; 2017. Available from:
  6. Girgis ST, Marks GB, Downs SH et al. Thunderstorm-associated asthma in an inland town in south-eastern Australia. Who is at risk? Eur Respir J 2000; 16: 3-8.
  7. Marks GB, Colquhoun JR, Girgis ST, et al. Thunderstorm outflows preceding epidemics of asthma during spring and summer. Thorax. 2001; 56: 468-71.
  8. D'Amato G, Vitale C, D'Amato M et al. Thunderstorm-related asthma: what happens and why. Clin Exp Allergy 2016; 46: 390-6.
  9. Victoria State Government Department of Health and Human Services. The November 2016 Victorian epidemic thunderstorm asthma event: an assessment of the health impacts. The Chief Health Officer’s Report, 27 April 2017. Melbourne: Victorian Government; 2017.
  10. Thien F, Beggs PJ, Csutoros D et al. The Melbourne epidemic thunderstorm asthma event 2016: an investigation of environmental triggers, effect on health services, and patient risk factors. Lancet Planet Health 2018; 2: e255-e63. Available from:
  11. Andrew E, Nehme Z, Bernard S et al. Stormy weather: a retrospective analysis of demand for emergency medical services during epidemic thunderstorm asthma. BMJ 2017; 359: j5636. Available from:
  12. Lohia S, Schlosser RJ, Soler ZM. Impact of intranasal corticosteroids on asthma outcomes in allergic rhinitis: a meta-analysis. Allergy. 2013; 68: 569-79. Available from:
  13. O'Hehir RE, Varese NP, Deckert K et al. Epidemic thunderstorm asthma protection with five-grass pollen tablet sublingual immunotherapy: a clinical trial. Am J Respir Crit Care Med 2018; 198: 126-8. Available from: