What Is Asthma?

Reviewed by: HU Medical Review Board | Last reviewed: February 2024

Asthma is a chronic (long-term) condition that affects the airways. It causes wheezing and difficulty breathing. Many people with asthma experience sudden intense symptoms. These are called asthma attacks. They are often triggered by something that bothers the lungs.1,2

Avoiding triggers and taking medicine can control symptoms. Work with your doctor to create an asthma action plan. This plan should detail when to take certain medicines. It can also include triggers to avoid.3

How common is asthma?

Asthma is a very common airway condition. Worldwide, about 260 million people have asthma. About 40 million people are diagnosed every year. The percentage of people who have asthma varies greatly by country.4,5

In the United States, about 1 in 12 people have asthma. This is more than 27 million Americans. About 4.5 million children in the US have asthma. In the US, asthma is more likely among:6,7

  • Boys under 18 years old, compared to girls under 18 years old
  • Adult women, compared to adult men
  • Black and Indigenous American adults
  • People with lower incomes
  • People who live in the Northeast, compared to those who live in the South and West

Asthma accounts for 5 million doctor visits and 1 million emergency room visits in the United States every year. Black Americans are 6 times more likely than white Americans to visit the emergency room for asthma. Black Americans are also 3 times more likely to die from asthma than white Americans.7

Current treatments are improving outcomes for people with asthma. It is becoming less common to have an asthma attack, be hospitalized, or die because of asthma.6,7

What causes asthma?

Asthma symptoms happen because of inflammation of the airways. Inflammation can cause airways to become narrow, overly sensitive, or blocked. When this happens, it becomes harder for air to get in and out of the lungs.1,8

We do not yet know all the causes of airway inflammation in asthma. In many people with asthma, an overactive immune system causes inflammation called “type 2.” We do not know why people with asthma have this immune response.9

Having a relative with asthma increases the risk of having asthma. So asthma may have a genetic or hereditary cause. Other factors that increase the risk of developing asthma include:8,10

  • Having another allergic condition, such as eczema or hay fever
  • Having higher body weight
  • Being a smoker or exposure to secondhand smoke
  • Exposure to exhaust fumes or other pollution

What are common symptoms of asthma?

Symptoms of asthma vary for each person. Some people may have symptoms all the time. Other people have less frequent asthma attacks. Other people may have symptoms only after exposure to a trigger. For some people, symptoms are worse at certain times of the day.11

Symptoms of asthma are similar to other respiratory conditions. Common symptoms include:12,13

  • Shortness of breath
  • Pain or tightness in your chest
  • Wheezing when exhaling

What can trigger asthma attacks?

In asthma, airways become more sensitive. Exposure to triggers can cause the airways to narrow, causing symptoms to flare. This is called an asthma attack. About 40 percent of people with asthma have had an asthma attack in the past year.6,7,12

Asthma triggers vary from person to person. Different types of asthma are defined based on the trigger. Common triggers include:2,12

  • Allergens, such as pollen, mold, or pet dander
  • Respiratory infections, such as the common cold
  • Cold air
  • Air pollutants and irritants, such as tobacco smoke or strong fragrances
  • Physical activity
  • Certain medicines
  • Strong emotions and stress

How is asthma diagnosed?

Your doctor can diagnose asthma based on symptoms, physical exams, and lung function tests. The doctor will ask questions about your symptoms, like how often you have them and how strong they are. The answers to these questions will help your doctor diagnose your asthma as intermittent, mild, moderate, or severe.12,13

Your doctor may also perform a spirometry test. This test checks how much air you can exhale and how quickly you can exhale it.12,13

Your asthma history and other tests help your doctor choose the best treatment and track symptoms over time.12,13

How is asthma treated?

Most people with asthma can control symptoms by taking medicine and avoiding triggers. With the right treatment, people can have few symptoms and participate in their usual activities. Controlling symptoms reduces the risk of asthma attacks and hospitalizations.12,14

The right medicine depends on a number of individual factors. Long-term drugs (such as inhaled corticosteroids) control symptoms on a day-to-day basis. They lower your risk of having an asthma attack. Quick-relief drugs (such as short-acting beta agonists) help relieve symptoms during an asthma attack.12,14

Many doctors follow a stepwise approach to asthma treatment. They will increase or decrease your medicine based on your symptoms. Talk to your doctor if you still have symptoms while taking drugs they prescribe.14

Is it possible to outgrow asthma?

Asthma is a chronic condition. But many children with asthma seem to “outgrow” their symptoms. It is not possible to predict who will outgrow their symptoms. As many as 3 out of 4 children with mild asthma do not have symptoms as adults.15

Children with more severe asthma are less likely to outgrow symptoms. Adults with asthma are also less likely to outgrow their symptoms.15

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