What Is Asthma?

Reviewed by: HU Medical Review Board | Last reviewed: December 2022 | Last updated: September 2023

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. How common asthma is in the population varies greatly between countries. Asthma is most common in:4,5

  • Australia
  • New Zealand
  • Central America
  • The United Kingdom

In the United States, about 1 in 13 people have asthma. This is about 25 million Americans. In the United States, asthma is more likely among:6

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

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

What causes asthma?

Asthma symptoms happen because of inflammation of the airways. This 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

We do not yet know all the causes of airway inflammation in asthma. In many people with asthma, an overactive immune system causes a response called “type 2 inflammation.” We do not know why people with asthma have this immune response.7

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

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

What are common symptoms of asthma?

The symptoms of asthma vary from 1 person to another. Some people may have symptoms all the time. Other people may 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.9

Common symptoms of asthma include:10

  • 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 half of people with asthma have had an asthma attack in the past year.6,10

Asthma triggers vary from person to person. Different types of asthma are defined based on the trigger. Common triggers include:2,10

  • Allergens, such as pollen, mold, or pet dander
  • Respiratory infections, such as the common cold
  • Cold air
  • Air pollutants
  • 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. They will ask questions about your symptoms, like how often you have the symptoms and how strong they are. The severity and frequency of your asthma flares will help your doctor diagnose your asthma as intermittent, mild, moderate, or severe.10,11

However, symptoms of asthma are similar to other respiratory conditions. To help diagnose asthma, doctors may perform a spirometry test. This test checks how much air you can exhale and how quickly you can exhale it.10,11

Your asthma history and other tests help your doctors choose the best treatment and track symptoms over time.10,11

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 normal activities. Controlling symptoms reduces the risk of asthma attacks and hospitalizations.10,12

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.10,12

Many doctors follow a stepwise approach to asthma treatment. This means they will increase or decrease your medicine based on your symptoms. Talk to your doctor if you still have symptoms while taking the drugs they prescribe.12

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.13

Children with more severe asthma are less likely to outgrow symptoms. Adults with asthma are also less likely to outgrow their symptoms.13

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