Asthma is a chronic respiratory disease that causes inflammation and narrowing of the airways, making it difficult to breathe.
There are four main categories of asthma based on severity, as classified by the National Asthma Education and Prevention Program:
- Intermittent
- Mild persistent
- Symptoms occur three to six times a week
- Nighttime symptoms occur three to four times a month
- Asthma attacks affect daily activities
- Lung function tests are normal when a person is not having an asthma attack
- Moderate persistent
- Symptoms occur daily
- Symptoms interfere with normal activities
- Nighttime symptoms more than once per week but not every day
- Asthma attacks affect daily activities
- Lung function tests are abnormal
- Severe persistent
- Symptoms occur throughout the day, every day, and severely limit daily activities
- Nighttime symptoms occur frequently, sometimes every night
- Lung function tests are abnormal
Asthma can also be classified by whether it is allergic or non-allergic:
- Allergic asthma is triggered by exposure to an allergen, such as pollen or pet dander
- Non-allergic asthma is triggered by factors such as stress, illness, extreme weather, irritants in the air, and some medications
There are also numerous types of asthma, including:
- Adult-onset asthma in which symptoms don’t start until patients are adults
- Exercise-induced bronchoconstriction (EIB, also sometimes called exercise-induced asthma)
- Occupational asthma, usually occurs in people who work around chemical fumes, dust or other irritants in the air
- Chronic obstructive pulmonary disease (COPD) is a collection of lung diseases breathing problems and obstruct airflow and includes refractory (severe) asthma
What Are Symptoms of Asthma?
Symptoms of asthma include:
- Difficulty breathing
- Shortness of breath
- Wheezing
- Chest tightness
- Coughing, especially at night or early morning, during exercise, or when laughing
Asthma symptoms may:
- Come and go over time
- Start or worsen with viral infections, such as a cold
- Worsen at in the morning or at night
Asthma attacks refer to episodes of significantly worsening symptoms that require a change in usual treatment. Asthma attacks may come on either gradually or suddenly and can be life-threatening.
What Causes Asthma?
The cause of asthma is unknown, but it usually results from a strong immune system response to a substance in the lungs.
Common triggers for asthma symptoms include:
- Allergies (such as pollen, ragweed, dust mites, mold, or animal dander)
- Irritants in the air (such as smoke, strong odors, chemical fumes)
- Extreme weather conditions
- Cold air
- Exercise
- Illness, particularly respiratory illness or the flu
- Stress
- Panic
- Strong emotions that can affect normal breathing patterns, such as laughing, crying, or shouting
- Certain medications
- Some foods
How Is Asthma Diagnosed?
Asthma is diagnosed with a patient history and a physical exam, which includes the doctor listening to a patient’s breathing and checking for allergic skin conditions.
Tests used to help diagnose asthma or rule out other causes for symptoms include:
- Pulmonary function tests
- Spirometry
- Bronchoprovocation tests
- Peak expiratory flow (PEF)
- Fractional exhaled nitric oxide (FeNO) tests
- Provocation (trigger) tests
- Exercise challenge
- Irritant challenge
- Methacholine challenge
- Allergy skin or blood tests, in patients who have a history of allergies
Diagnosing asthma in children younger than 6 can be difficult, since young children are usually unable to perform a pulmonary function test such as spirometry. Asthma medicines may be tried for a few months to see how the child responds.
What Is the Treatment for Asthma?
Asthma is usually treated with quick-relief and long-term control medicines. Allergy shots (immunotherapy) may also be helpful.
Quick-relief medications are bronchodilators that expand the airways, and are taken at the first sign of asthma symptoms for immediate relief:
- Short-acting inhaled beta2-agonists (inhalers)
- Anticholinergics
Long-term asthma control medications are taken daily to prevent symptoms and asthma attacks and include:
- Inhaled corticosteroids
- Fluticasone
- Budesonide
- Mometasone
- Beclomethasone
- Ciclesonide
- Antileukotrienes or leukotriene modifiers
- Montelukast sodium
- Zafirlukast
- Zileuton
- Long-acting inhaled beta2-agonists (usually combined with an inhaled corticosteroid)
- Formoterol
- Salmeterol
- Vilanterol
In severe cases, when traditional treatments do not work well enough other therapies may be used, such as:
- Biologics
- Benralizumab (Fasenra)
- Dupilumab (Dupixent)
- Mepolizumab (Nucala)
- Omalizumab (Xolair)
- Reslizumab (Cinqair)
- Oral corticosteroids
- Prednisone
- Dexamethasone
- Methylprednisolone
- Immunotherapy, useful when asthma is triggered by an allergy
- Allergy shots (subcutaneous immunotherapy [SCIT])
- Sublingual (under the tongue) tablets or drops (sublingual immunotherapy [SLIT])
From 
https://www.nhlbi.nih.gov/health-topics/asthma
https://www.healthdirect.gov.au/complications-of-asthma
https://www.nhlbi.nih.gov/health-topics/asthma