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What is asthma?

Asthma is the term for a group of diseases characterized by episodes of airway obstruction. Airways affected by asthma are chronically inflamed and sometimes narrowed, making breathing difficult. An acute asthma attack can be triggered by a respiratory infection, medications such as aspirin or beta-blockers, or by inhaling an irritant, such as perfume or polluted air (bronchial hyperresponsiveness).1,2 During an acute asthma attack, patients may experience chest tightness, cough or wheeze, or feel short of breath.
Asthma can develop in a variety of ways depending on the interaction between many environmental and genetic factors.3 This condition is one of the most common respiratory diseases; in 2016, a reported 8.3% of Americans had asthma.4

is an excessive contraction of the airways, and involves an exaggerated response to various inhaled stimuli.20

What are common symptoms?

Common asthma symptoms include:

  • Coughing, wheezing, breathlessness, or chest tightness,5 all of which can vary over time and intensity.
  • Excessive variation in lung function, which are changes in expiratory airflow compared to those seen in healthy people.6
  • Airway hyper-responsiveness to stimuli such as exercise and inhaled irritants.7

Severe asthma can limit a patient’s physical activity and disrupt their sleep.8 Because symptoms vary in duration and intensity, asthma is typically classified by severity, including the following9:

  • Intermittent
  • Mild persistent
  • Moderate persistent
  • Severe persistent

What are the causes?

Several factors have been proposed as causes for developing asthma, though there is no defined cause for the disease. Risk factors for asthma include genetic, environmental, and host factors.10

Other common risk factors include11:

  • Air pollution
  • Alcohol consumption
  • Obesity
  • Psychosocial factors
  • Respiratory disease history (i.e.: rhinitis, sinusitis)
  • Smoking

How does this topic relate to my microbiome?

Several studies of asthmatic patients have revealed diverse microbial communities in their airways, with dysbiosis in their lower airways.12 For example, asthmatic patients can have an increased abundance of Proteobacteria phylum.12,13 Despite these findings, it’s not yet clear if these changes are a cause of asthma or a consequence of the disease.14

On the other hand, exposure to microbially rich environments during childhood – like growing up on a farm, or the presence of older siblings or two or more dogs – has been associated with lower rates of asthma.13

is a term for an imbalance in microbiota composition or function.

Which diseases/topics are related to asthma?

People who have asthma may be at an increased risk of other comorbidities, including 15,16:

  • Anxiety
  • Chronic obstructive pulmonary disease (COPD)
  • Constipation
  • Coronary heart disease
  • Depression
  • Hypertension
  • Indigestion
  • Irritable bowel syndrome (IBS)
  • Pneumonia

How can I take action?

An asthma diagnosis is based on characteristic patterns of respiratory symptoms, such as wheezing, shortness of breath, chest tightness, and variable expiratory airflow limitation. The pattern of symptoms is important, since respiratory symptoms may be due to other acute or chronic conditions. It’s important to consult your doctor if any of these symptoms appear. Depending on the severity of your symptoms, management may include17:

  • Identification and avoidance of trigger factors (exercise, allergen or irritant exposure, weather changes, or viral respiratory infections)
  • Medications such as inhaled bronchodilators or steroids
  • Monitoring of symptoms
  • Patient education
  • Increasing prebiotic fiber intake or taking probiotic supplements, since these have been shown to reduce airway inflammation in patients with asthma18,19


1. Martinez, F. D., & Vercelli, D. (2013). Asthma. The Lancet, 382(9901), 1360–1372.

2. Wenzel, S. E. (2012). Asthma phenotypes: the evolution from clinical to molecular approaches. Nature Medicine, 18(5), 716–725.

3. Sullivan, A., Hunt, E., MacSharry, J., & Murphy, D. M. (2016). The Microbiome and the Pathophysiology of Asthma. Respiratory Research, 17(1), 163.

4. July 4, 2018. Center for Disease Control and Prevention. Most Recent Asthma Data.

5. Anderson, H. M., & Jackson, D. J. (2017). Microbes, allergic sensitization, and the natural history of asthma. Current Opinion in Allergy and Clinical Immunology, 17(2), 116–122.

6. Tantucci, C. (2013). Expiratory flow limitation definition, mechanisms, methods, and significance. Pulmonary Medicine, 2013, 1–6.

7. Holgate, S. T., Wenzel, S., Postma, D. S., Weiss, S. T., Renz, H., & Sly, P. D. (2015). Asthma. Nature Reviews Disease Primers, 10(1), 15025.

8. Globe, G., Martin, M., Schatz, M., Wiklund, I., Lin, J., von Maltzahn, R., & Mattera, M. S. (2015). Symptoms and markers of symptom severity in asthma—content validity of the asthma symptom diary. Health and Quality of Life Outcomes, 13(1), 21.

9. Pollart, S. M., & Elward, K. S. (2009). Overview of changes to asthma guidelines: diagnosis and screening. American Family Physician, 79(9), 761–767.

10. Subbarao, P., Mandhane, P. J., & Sears, M. R. (2009). Asthma: epidemiology, etiology and risk factors. Canadian Medical Association Journal, 181(9), E181–E190.

11. Ilmarinen, P., Tuomisto, L. E., & Kankaanranta, H. (2015). Phenotypes, Risk Factors, and Mechanisms of Adult-Onset Asthma. Mediators of Inflammation, 2015, 1–19.

12. Fujimura, K. E., & Lynch, S. V. (2015). Microbiota in Allergy and Asthma and the Emerging Relationship with the Gut Microbiome. Cell Host & Microbe, 17(5), 592–602.

13. Huang, Y. J., & Boushey, H. A. (2015). The microbiome in asthma. Journal of Allergy and Clinical Immunology, 135(1), 25–30.

14. Legatzki, A., Rösler, B., & von Mutius, E. (2014). Microbiome Diversity and Asthma and Allergy Risk. Current Allergy and Asthma Reports, 14(10), 466.

15. Lisspers, K., Janson, C., Larsson, K., Johansson, G., Telg, G., Thuresson, M., & Ställberg, B. (2018). Comorbidity, disease burden and mortality across age groups in a Swedish primary care asthma population: An epidemiological register study (PACEHR). Respiratory Medicine, 136, 15–20.

16. Weatherburn, C. J., Guthrie, B., Mercer, S. W., & Morales, D. R. (2017). Comorbidities in adults with asthma: Population-based cross-sectional analysis of 1.4 million adults in Scotland. Clinical & Experimental Allergy, 47(10), 1246–1252.

17. July 5 2018. Global Strategy for Asthma, 2018 GINA Report, Global Strategy for Asthma Management.

18. Vliagoftis, H., Kouranos, V. D., Betsi, G. I., & Falagas, M. E. (2008). Probiotics for the treatment of allergic rhinitis and asthma: systematic review of randomized controlled trials. Annals of Allergy, Asthma & Immunology, 101(6), 570–579.

19. Halnes, I., Baines, K., Berthon, B., MacDonald-Wicks, L., Gibson, P., & Wood, L. (2017). Soluble Fibre Meal Challenge Reduces Airway Inflammation and Expression of GPR43 and GPR41 in Asthma. Nutrients, 9(1), 57.

20. Grootendorst, D. C., & Rabe, K. F. (2004). Mechanisms of Bronchial Hyperreactivity in Asthma and Chronic Obstructive Pulmonary Disease. Proceedings of the American Thoracic Society, 1(2), 77–87.