Asthma is a chronic lung condition that affects millions of people worldwide. Nearly 25 million people in the United States had asthma in 2018, including approximately 5.5 million children. Globally, an estimated 339 million people have asthma.

What Is Asthma?

Asthma is a chronic pulmonary disease that causes periodic or persistent breathing problems, including shortness of breath, wheezing, and coughing. While asthma is incurable, it is highly manageable. Asthma is treated with maintenance medications that keep symptoms under control and rescue medications for severe episodes. Severe asthma can be life-threatening and may require emergency intervention and hospitalization.

What Causes Asthma?

The cause of asthma is not well understood. Most researchers believe asthma develops because of a combination of genetic and environmental risk factors. Asthma is often an allergic reaction related to an overreaction by the immune system in response to a substance that enters the lungs.

Some risk factors for developing asthma include:

• Age
• Family history of asthma
• Race and ethnicity
• Early childhood exposure to secondhand smoke
• Air pollution
• Occupational hazards
• Other health conditions, like allergies and eczema

Some common triggers of asthma attacks include:

• Tobacco smoke
• Pet dander
• Allergens, such as dust mites, mold, or pollen
• Air pollution
• Pests, such as cockroaches or mice
• Fumes from detergents, cleaning products, or disinfectants
• Exercise or physical activity
• Viral infections
• Strong emotions

Read more about the causes of asthma.

How Is Asthma Diagnosed?

Diagnosing asthma requires a physical examination and pulmonary function tests. An official diagnosis may require seeing specialists, such as a pulmonologist (lung specialist) or an allergist.

Medical History and Physical Exam

Your doctor or your child’s pediatrician will take a thorough medical history. They will ask questions about symptoms, risk factors for asthma, and family history. As part of a physical exam, your health care provider may examine your nose, throat, and ears and listen to your breathing. They may also examine your skin for eczema or symptoms of an allergic reaction.

Pulmonary Function Tests

Pulmonary function, or lung function, tests help diagnose asthma and other respiratory diseases. The tests below are commonly used to diagnose asthma.

Spirometry

Spirometry assesses airway obstruction. It is the primary test used to diagnose asthma in adults and children over the age of 5. The test is performed by breathing into a tube attached to a machine (called a spirometer) that measures how much air you can exhale and how quickly you can exhale.

Exhaled Nitric Oxide Test

An exhaled nitric oxide test detects inflammation in the airways. High levels of nitric oxide, a gas produced by the lungs, can indicate airway inflammation — a potential sign of asthma.

Challenge Tests

Challenge tests may be used when spirometry tests don’t show definitive results. They are often performed by an asthma specialist to ensure safety. A challenge test is performed by triggering asthma symptoms. Lung function tests are performed before and after asthma symptoms are triggered. You will always be given medication to stop symptoms after the challenge is complete.

Diagnosing Asthma in Children

Pulmonary function tests are difficult to perform in children age 5 and under. Doctors generally rely on parental reports of symptoms rather than lung function tests. Depending on the severity of a child’s symptoms, a doctor may prescribe an asthma treatment to see how a child responds.

Your child’s pediatrician may refer you to a pediatric asthma specialist.

Learn more about asthma diagnosis.

What Are the Symptoms of Asthma?

Asthma symptoms can range from mild to severe and can be persistent or intermittent. Some symptoms can be managed with asthma medications at home, while others may be life-threatening. Common symptoms of asthma include both respiratory (breathing-related) and nonrespiratory symptoms, like fatigue and anxiety.

Shortness of Breath

Shortness of breath, also called dyspnea, is a sensation of being unable to breathe enough air. It is a common symptom of most types of asthma.

Wheeze

Wheezing is a whistling sound when breathing. Wheezing occurs when the bronchial tubes (tubes that carry air to the lungs) narrow. Mild wheezing occurs when a person exhales. During a more serious asthma attack, wheezing can occur when a person inhales and exhales.

Cough

Chronic coughing can be a symptom of asthma. Usually asthma-related coughing doesn’t produce mucus. Asthma-related coughing often occurs at night. It can also be triggered by physical activity, allergens, or irritants like smoke.

Chest Tightness

Chest tightness can make it difficult to take a full breath and can be an early sign of an asthma exacerbation. Chest tightness can be worse when exposed to cold air or when exercising.

Chest Pain

Chest pain can be a symptom of asthma attacks. Asthma-related chest pain is often felt in the sternum.

Trouble Breathing

Rapid breathing, a high-pitched noise when inhaling, taking a long time to exhale, and sniffing the air are all signs of severe breathing difficulty.

Intercostal Retractions

The intercostal muscles are muscles between the ribs that allow the rib cage to expand and contract. Intercostal retractions occur when the intercostal muscles pull inward. Retractions may occur if the trachea (windpipe) or bronchioles (airways in the lungs) are blocked. Seek immediate medical care in the event of intercostal retractions.

Nonrespiratory Symptoms

Other symptoms of asthma or asthma attacks include:

• Trouble sleeping
• Fatigue
• Sweating
• Rapid pulse
• Anxiety
• Depression

Recognizing an Asthma Attack

Asthma attacks can be mild, moderate, or severe. Mild attacks can often be managed at home while severe asthma attacks may require emergency medical care.

Mild Asthma Attack Symptoms

• Mild shortness of breath when walking
• No shortness of breath when stationary
• Ability to speak normally
• Ability to lie flat
• Mild wheezing

Moderate Asthma Attack Symptoms

• Shortness of breath when stationary
• Ability to speak in phrases, but not in full sentences
• Must sit up
• Audible wheezing
• Intercostal retractions

Severe Asthma Attack Symptoms

Contact your doctor or seek medical care in the event of an acute severe exacerbation.

• Severe shortness of breath
• Ability to say only single words
• Loud wheezing
• Must sit up
• Sweating
• Rapid pulse
• Severe intercostal retractions

Call 911 or emergency services immediately in the following circumstances:

• Sudden wheezing in response to an allergen
• Severe breathing difficulties
• Bluish tinge to face and lips when not coughing
• Fainting

What Are the Different Types of Asthma?

Asthma can be categorized by triggers and by severity.

Asthma Types by Trigger

Symptoms of asthma can be triggered by a wide variety of substances, situations, and underlying health conditions. It is possible to have more than one type of asthma.

Allergic Asthma

Allergic asthma is the most common type of asthma, comprising about 60 percent of asthma cases in the United States. It is most prevalent in early childhood. Allergic asthma is caused by an overreaction of the immune system in response to an allergen, like pollen, furry pets, mold, cockroaches, and dust mites.

Nonallergic Asthma

Nonallergic asthma makes up about 70 percent of cases of adult-onset asthma. It can be more difficult to identify what triggers symptoms in nonallergic asthma. Possible triggers include stress, medications, food additives, cold air, and air pollution.

Exercise-Induced Bronchoconstriction

Approximately 90 percent of people with asthma will experience exercise-induced bronchoconstriction, also known as EIB or exercise-induced asthma. In people with EIB, exercise triggers bronchoconstriction — the narrowing of airways in the lungs. Bronchoconstriction in turn triggers asthma symptoms, like shortness of breath or wheezing.

Occupational Asthma

People who work in jobs where they are exposed to airborne irritants, such as fumes or dust, may develop occupational asthma. Occupational asthma accounts for 15 percent to 23 percent of adult-onset asthma cases in the U.S. Bakers, farmers, laboratory workers, and people who work manufacturing metals and plastics are at greater risk of developing occupational asthma.

Other Types of Asthma

Some less common types of asthma include:

• Asthma-COPD overlap syndrome
• Aspirin-exacerbated respiratory disease (AERD)
• Eosinophilic asthma

Learn more about types of asthma.

Asthma Types by Symptom Severity

In addition to categorization by asthma triggers, asthma is classified by the frequency of symptoms and how much they impact daily life. Asthma severity is used by health care providers to determine which asthma medications are most appropriate. Your asthma classification can change over time. It is possible to have a severe asthma attack no matter how your asthma is classified.

Your asthma severity may fall into one of the following categories:

• Intermittent asthma
• Mild persistent asthma
• Moderate persistent asthma
• Severe persistent asthma or severe asthma

Read more about the different types of asthma.

How Is Asthma Treated?

There are two primary categories of asthma treatment: rescue medications and maintenance medications. Lifestyle habits can also help you control asthma symptoms and avoid severe episodes.

If you or your child has asthma, it’s important to develop an asthma action plan with your doctor or your child’s pediatrician. An asthma action plan outlines the treatment protocol when asthma is well-controlled and when you or your child are experiencing worsening symptoms.

Maintenance Medications

Maintenance medications, also called long-term control medications, are generally taken daily to keep asthma symptoms under control and prevent asthma attacks. They can be administered using an inhaler or nebulizer or with oral medications.

There are several categories of asthma-control medications, including:

• Inhaled corticosteroids
• Combination medications
• Leukotriene modifiers
• Biologic immunomodulators

Rescue Medications

Rescue medications are used to quickly relieve the symptoms of asthma attacks. They are generally used on an as-needed basis to treat acute asthma symptoms. Using rescue medications regularly may indicate that your asthma is not well-controlled.

The most common rescue medications are short-acting beta-agonists (SABAs) like albuterol. In severe cases, oral steroids like prednisone and methylprednisolone may be prescribed for a short duration.

Side effects are possible with all asthma medications. Talk to your doctor about what to expect from the medications you are prescribed.

Lifestyle Changes

Changing certain habits can help you manage asthma by avoiding common triggers. Lifestyle habits are not a replacement for maintenance asthma medications, but they can help decrease the amount of medications you may need. Some examples of lifestyle adjustments include:

• Increasing cleaning to minimize household allergens, like dust mites and pet dander
• Finding ways to manage stress, which can trigger asthma
• Avoiding foods that cause allergic reactions
• Avoiding foods or additives that trigger asthma symptoms, like sulfites
• Quitting smoking and avoiding exposure to secondhand smoke
• Avoiding irritants that trigger asthma, such as strong cleaning chemicals and diesel exhaust fumes

Changes like reducing stress and quitting smoking can have a positive effect on overall quality of life.

How Do Other Conditions Affect Asthma?

Certain health conditions are more common in people with asthma than in the general population. Below are some common comorbidities for people with asthma.

Allergies

The tendency to develop asthma, atopic dermatitis (also known as eczema), and allergies is called atopy. These conditions all involve an overreaction by the immune system in response to common allergens.

Respiratory Conditions

Asthma can raise the risk for developing some other respiratory and pulmonary conditions, including:

• Asthma-COPD overlap syndrome
• Aspirin-exacerbated respiratory disease
• Obstructive sleep apnea

People with asthma are at greater risk of developing serious complications from the flu, including developing a respiratory infection like pneumonia. People with moderate to severe asthma may have a higher risk for severe illness if they become infected with the new coronavirus that causes COVID-19.

Learn more about health conditions related to asthma.

Asthma Condition Guide

• Symptoms of Asthma
• Asthma — The Path to Diagnosis
• Types of Asthma
• What Causes Asthma?
• Conditions Related To Asthma
• Treatments for Asthma