Asthma is a chronic inflammatory disease of the respiratory system characterized by bronchial hyperresponsiveness, episodic acute asthma exacerbations, and reversible airflow obstruction. Allergic (extrinsic) asthma usually develops in childhood and is triggered by allergens such as pollen, dust mites, and certain foods. Nonallergic (environmental or intrinsic) asthma usually develops in patients over the age of forty and can have various triggers, such as cold air, medications (e.g., aspirin), exercise, and viral infections. The cardinal symptoms of asthma are intermittent dyspnea, cough, and high-pitched expiratory wheeze. Symptoms remit in response to antiasthmatic medications or resolve spontaneously upon removal of the trigger. In a patient with , diagnosis is confirmed by demonstrating reversible bronchial obstruction on pulmonary function tests. Additional tests may be required to evaluate for asthma triggers and comorbidities that increase the risk of acute exacerbations. Treatment regimens differ based on the severity of asthma but primarily consist of different combinations of beta-2 agonists and inhaled corticosteroids (ICS). Systemic corticosteroids are usually reserved for patients with severe persistent asthma. To achieve symptomatic control and minimize the risk of exacerbations, comorbidities should be managed and exposure to asthma triggers minimized Follow-ups are essential to monitor the response to therapy and to adjust treatment regimens in a stepwise manner.
“” are discussed in their own article.
- Asthma: a chronic inflammatory disease of the respiratory system characterized by bronchial hyperresponsiveness, episodic exacerbation (asthma attacks), and reversible airflow obstruction; manifests with reversible cough, wheezing, and dyspnea
- Acute asthma exacerbation: a reversible worsening of the clinical features of asthma that develops over a short period of time and can progress to life-threatening asthma; may be the first manifestation of asthma in some patients
- Allergic asthma: the most common type of asthma; begins with intermittent symptoms in childhood and is usually associated with atopy (e.g., eczema, rhinitis) and a good response to treatment
- Nonallergic asthma: an uncommon type of asthma that is not related to atopy and is typically associated with a poor response to standard treatment (e.g., ICS)
- See also “Subtypes and variants.”
- 5–10% of the US population
- More common in black than white patients
- For unknown reasons, the prevalence of asthma has been increasing over the past 20 years. 
- Sex: differs depending on age of onset
- Age of onset
Epidemiological data refers to the US, unless otherwise specified.
- The exact etiology of asthma remains unknown.
- Risk factors for asthma include:
- See also .
- Several factors can trigger an initial asthma attack or cause acute asthma exacerbation.
|Allergic asthma |
|Nonallergic asthma |
Childhood exposure to second-hand smoke increases the risk of developing asthma!.
Common underlying pathophysiology
Asthma is an inflammatory disease driven by T-helper type 2 cells (Th2-cell) that manifests in individuals with a genetic predisposition. It consists of the following three pathophysiologic processes:
- Bronchial hyperresponsiveness
- Symptoms are primarily caused by inflammation of the terminal bronchioles, which are lined with smooth muscle but lack the cartilage found in larger airways.
- Overexpression of Th2-cells → inhalation of antigen results in production of cytokines (IL-3, IL-4, IL-5, IL-13) → activation of eosinophils and induction of cellular response (B-cell IgE production) → bronchial submucosal edema and smooth muscle contraction → bronchioles collapse 
- Endobronchial obstruction caused by:
- Allergic asthma
- Irritant asthma: irritant enters lung → ↑ release of neutrophils → submucosal edema → airway obstruction
- (NSAID-exacerbated respiratory disease) is characterized by the Samter triad:
- Typical features: The following features are usually intermittent and can occur either sporadically or in response to an .
- Atypical features: See “Subtypes and variants.”
- Features of common comorbid conditions (e.g., atopic conditions like allergic rhinitis, or eczema)
- is covered in detail separately.
Characteristic examination findings may not be present between episodes of asthma exacerbation!
Subtypes and variants
- Exercise-induced asthma: asthma in which bronchoconstriction is triggered by physical exertion; treated with inhaled SABAs shortly prior to exercise and reduction of potential environmental triggers (e.g., cold air, allergens) 
- Adult-onset asthma: an uncommon phenotype in which patients present with symptoms for the first time in adulthood; more likely to be nonallergic and involves a poor response to standard treatment
- Cough variant asthma: : a form of asthma in which the predominant symptom is chronic dry cough, without other characteristic symptoms of asthma (e.g., wheezes, congestion, dyspnea)
General principles 
- Asthma can be diagnosed in patients ≥ 5 years of age, based on a combination of: 
- Consider adjunctive studies as needed:
- To identify common comorbidities
- To exclude
- are covered separately.
Pulmonary function testing 
- Characteristic findings (observable using any of the PFT modalities described below)
|Diagnostic testing in asthma |
|PFT modality||Supportive findings||Test characteristics|
|Peak flow meter (PFM)|
- Allergy workup: Consider if allergens are suspected to play a significant role in exacerbations.
- Evaluation for additional asthma triggers: e.g., see “Rhinitis”, “Sinusitis”, “GERD” 
Additional diagnostic studies (not routinely recommended)
- Sputum analysis revealing one or more of the following:
- normal or ↑ DLCO:
- FeNO): may be elevated in allergic asthma  (
- The main alternate COPD; differentiating features are detailed below. to consider is
- See also “ ,” “ ,” and “ ” for other conditions that can mimic asthma.
Comparison of asthma and COPD
|Age at diagnosis|| |
|Etiology|| || |
|Clinical presentation|| || |
|Bronchial obstruction|| || |
The differential diagnoses listed here are not exhaustive.
General principles 
- Long-term management of asthma involves a combination of treatment, close follow-up, and patient education.
- Goals for managing asthma
- Symptom control with and adjunctive therapy
- Reducing the risk of exacerbations
- Specific asthma variants and phenotypes (e.g., exercise-induced asthma) require tailored treatment.
- For the management of exacerbations, see “Acute asthma exacerbation.”
The key to long-term asthma management is a continuous cycle of clinical assessment and treatment adjustment.
- Confirm .
- Assess severity (see “ ”).
- Initiate based on severity.
- Manage comorbidities; reduce exposure to asthma triggers (see “Adjunctive therapy”).
- Monitor response to therapy.
- Adjust treatment (step up or step down) based on response to therapy.
- Schedule frequent follow-ups.
Long-term follow-up and reassessment of asthma symptom control are recommended every 1–6 months.
Assessment of severity
The National Asthma Education and Prevention Program (NAEPP) guidelines classify asthma severity as intermittent or persistent in individuals who have not yet been initiated on long-term therapy based on the following: 
- Symptom severity
- Degree of impairment in lung function
- Frequency and risk of exacerbations
- The 2020 Global Initiative for Asthma (GINA) guidelines classify severity into well-controlled, partly-controlled, and uncontrolled based on the minimum level of long-term treatment required to achieve symptom control (not detailed here). 
Classification of asthma severity in adults and children ≥ 12 years of age (NAEPP) 
The most severe category of any feature determines the severity.
|Class||Symptom severity||Lung function||Exacerbations requiring systemic corticosteroids|
|Intermittent asthma|| || |
|Mild persistent asthma|| || |
|Moderate persistent asthma|| |
|Severe persistent asthma|| |
- Different combinations of daily and rescue therapies are given in a stepwise fashion until symptoms are controlled. 
- In treatment-naive patients, the initial treatment regimen should be guided by the judgment, and patient preference. , clinical
- Consult asthma specialists for treatment of step 4 and higher; consider specialist consultation for step 3 treatment. 
- The recommendations here are consistent with the 2020 NAEPP guidelines; in areas in which they differ, the 2020 GINA guideline recommendations are also discussed.
- Treatment of patients ≥ 12 years is detailed here; regimens differ according to the patient's age (see “Tips & links” for guidance on management of asthma in infants and children < 12 years of age).
Stepwise pharmacological treatment of chronic asthma in adults and children ≥ 12 years old (NAEPP)
|Treatment steps|| |
Single inhalers are preferred for combination medications.
|Rescue inhaler (as needed)|
| || |
Step 2 (mild persistent asthma)
|Preferred|| || |
|Alternatives|| || |
Step 3 (moderate persistent asthma)
|Alternatives|| || |
Step 4 (moderate to severe persistent asthma)
|Alternatives|| || |
Step 5 (severe persistent asthma)
|Preferred|| || |
Step 6 (severe persistent asthma)
| || |
Any change in treatment regimen should be monitored closely with regular follow-ups.
General principles 
- The goal of antiasthmatic pharmacotherapy is to counteract bronchoconstriction by reducing bronchial inflammation and parasympathetic tone.
- Drugs effective in acute asthma exacerbation: SABAs, SAMAs, and systemic corticosteroids. 
- Drugs effective in the long-term management of asthma (i.e., not for acute management) 
Commonly used medications 
Overview of commonly used asthma medications 
Dosages detailed here are for adults or children ≥ 12 years of age
|Class||Examples||Mechanism and uses|
|Short-acting beta-2 agonists (SABA)|| |
|Long-acting beta-2 agonists (LABA)|| |
|Inhaled corticosteroids (ICS) |
|Leukotriene receptor antagonists (LTRAs)|| |
|Long-acting muscarinic antagonists (LAMA)|
|Short-acting muscarinic antagonists (SAMA)|
Inhaled corticosteroids do not take full effect until they have been used for approx. 1 week.
These medications are not commonly used in clinical practice. They are typically reserved for special cases under the guidance of a specialist.
Biologics for severe asthma (monoclonal antibodies)
- Omalizumab (anti-IgE antibody)
- Mepolizumab, reslizumab, benralizumab 
- Methylxanthines (e.g., theophylline)
Mast cell stabilizers (chromones): prevent release of inflammatory mediators from mast cells
- Examples: cromolyn sodium, nedocromil sodium
- Preventive treatment prior to exercise or unavoidable exposure to known allergens in patients ≥ 5 years old
- Not commonly used
- Leukotriene pathway modifiers (e.g., Zileuton)
Theophylline is no longer routinely prescribed due to the risk of toxicity. It is used solely as an adjunctive or alternative therapy.
- Reducing exposure to triggers or allergens
- Managing comorbidities
- Reducing the risk of infection-induced exacerbations
- Provide information and tools for self-monitoring and self-management (e.g., written action plan, peak flow meter).
- Encourage physical activity, especially in younger patients.
- Smoking cessation
Social interventions 
- Screen for systemic barriers to care and socioeconomic/environmental risk factors contributing to poor outcomes.
- Provide support to enhance access to care, treatment adherence, and sustainable functional improvement.
Special patient groups
- Asthma symptoms may be worse, better, or unchanged during pregnancy.
- Same stepwise management as with other patients
- Inhalation treatments preferred
- Poorly managed asthma can increase the risk of pregnancy complications (e.g., preeclampsia, premature birth, congenital abnormalities).
- Monthly monitoring of asthma is recommended.
Children under 5 years of age
- Asthma in patients under 5 years of age is challenging to diagnose and is often underdiagnosed, as children in this age group are not typically able to adequately perform the spirometric maneuvers.
- Regimens containing corticosteroids are preferred as initial therapy in infants and young children; see “Tips & links” for details on treatment regimens and dosages. 
- Young children (< 5 years) may require nebulizers because of difficulty using inhalers.