Asthma is a chronic (long-term) condition that affects the airways in the lungs. The airways are tubes that carry air in and out of your lungs. If you have asthma, the airways can become inflamed and narrowed at times.
Asthma affects people of all ages and often starts during childhood. You may wheeze, cough, or feel tightness in your chest. These symptoms can range from mild to severe and can happen every day or only once in a while. Certain things can set off or worsen asthma symptoms, such as cold air. These are called asthma triggers. When symptoms get worse, it is called an asthma attack.
An asthma action plan can help you manage your asthma. The plan may include monitoring, avoiding triggers, and using medicines.
Find asthma guides, tip sheets, and other resources from NHLBI’s Asthma Learn More Breathe Better program.
Causes - Asthma
The exact cause of asthma is unknown, and the causes may vary from person to person. However, asthma is often the result of a strong response of the immune system to a substance in the lungs. To understand asthma, it helps to understand How the Lungs Work.
Normally, the body’s immune system helps to fight infections. Sometimes a person’s immune system responds to a substance in the environment called an allergen. When someone breathes in an allergen, such as ragweed, the immune system in the airways may react strongly. Other people exposed to the same substance may not react at all.
The immune system reacts to an allergen by creating . Inflammation makes your airways swell and narrow and possibly produce more mucus. This can make it harder to breathe. The muscles around the airways may also tighten, which is called a bronchospasm. This can make it even harder to breathe.
Over time, the airway walls can become thicker. The image below shows how airways narrow during asthma.
Your asthma may have been caused partly by a viral infection or allergens in the air when you were a baby or young child. During this stage of life, your immune system is still developing.
It’s not clear why one person reacts to an exposure while others do not. Genes seem to play a role in making some people more susceptible to asthma.
Risk Factors - Asthma
Your environment or occupation, your family history or genes, other medical conditions, your race or ethnicity, or your sex may raise your risk for developing asthma.
Asthma affects people of all ages, but it often starts during childhood. Sometimes asthma develops in adults, particularly women. This type of asthma is called adult-onset or late-onset asthma.
Environment or occupation
Things in your environment, including at work or home, may raise your risk of developing asthma or make asthma symptoms worse.
- Exposure to cigarette smoke in the womb or in a child’s first few years raises the risk of developing asthma symptoms early in life. This exposure may also affect lung growth and development.
- Exposure to different in the environment, especially early in life, can affect how the immune system develops. These effects on the immune system may either increase or protect against the risk of developing asthma.
- Exposures that occur in the workplace, such as chemical irritants or industrial dusts, may also raise the risk of developing asthma in susceptible people. This type of asthma is called occupational asthma. It may develop over a period of years, and it often lasts even after you are no longer exposed.
- Poor air quality from pollution or allergens may make asthma worse. Pollutants may include traffic-related air pollution. Allergens in the air may include pollen, dust, or other particles.
Family history and genes
Genes may play a role in the development of asthma because they affect how the immune system develops. More than one gene is likely involved. You inherit genes from your parents. Having a parent who has asthma, especially if the mother has asthma, increases the risk that a child will develop asthma.
Other medical conditions
Asthma is often linked to other medical conditions, such as:
- Allergies. Asthma is usually a type of allergic reaction. People who have asthma often have other types of allergies. They may have food allergies or get a runny or stuffy nose from pollen. You may be at higher risk for developing asthma if you had allergic reactions in early childhood to substances in the air, such as pollen, dander, mold, or dust. The more things you are allergic to, the higher your risk of asthma.
- Obesity can increase the chances of developing asthma or worsening asthma symptoms. This may be because people who have obesity can have inflammation or changes in the immune system.
- Respiratory infections and wheezing. Young children who often have respiratory infections caused by viruses are at highest risk of developing asthma symptoms early in life.
Race or ethnicity
African Americans and Puerto Ricans are at higher risk of asthma than people of other races or ethnicities. African American and Hispanic children are more likely to die from asthma-related causes than non-Hispanic white Americans.
Among children, more boys than girls have asthma. Among teens and adults, asthma is more common among women than men.
Screening and Prevention - Asthma
Signs, Symptoms, and Complications - Asthma
How often signs and symptoms of asthma occur may depend on how severe, or intense, the asthma is and whether you are exposed to allergens. Some people have symptoms every day, while others have symptoms only a few days of the year. For some people, asthma may cause discomfort but does not interfere with daily activities. If you have more severe asthma, however, your asthma may limit what you are able to do.
When asthma is well controlled, a person shows few symptoms. When symptoms worsen, a person can have what is called an asthma attack, or an exacerbation. Over time, uncontrolled asthma can damage the airways in the lungs.
Signs and symptoms
Signs and symptoms of asthma may include:
- Chest tightness
- Coughing, especially at night or early morning
- Shortness of breath
- Wheezing, which causes a whistling sound when you exhale
While other conditions can cause the same symptoms as asthma, the pattern of symptoms in people who have asthma usually has some of the following characteristics.
- They come and go over time or within the same day.
- They start or get worse with viral infections, such as a cold.
- They are triggered by exercise, allergies, cold air, or from laughing or crying.
- They are worse at night or in the morning
Asthma attacks, or exacerbations, are episodes that occur when symptoms get much worse and require a change in typical treatment. These can come on gradually or suddenly and may be life-threatening. People who have severe asthma often get asthma attacks more often.
Diagnosis - Asthma
Asthma is diagnosed based on your medical history, a physical exam, and results from diagnostic tests. You may need to see a team of healthcare providers, including your doctor; an asthma specialist, called a pulmonologist; or an allergy specialist, called an allergist.
Medical history and physical exam
Your doctor will ask about your risk factors for asthma and your symptoms. They may ask also about any known allergies. This includes how often symptoms occur, what seems to trigger your symptoms, when or where symptoms occur, and if your symptoms wake you up at night.
During the physical exam, your doctor may:
- Listen to your breathing and look for symptoms of asthma
- Look for allergic skin conditions, such as eczema
Your doctor may ask you to perform the following tests to determine whether your symptoms are caused by asthma.
- Pulmonary function tests, such as spirometry, which involves breathing in and out through a tube connected to a computer. This measures how much and how fast the air moves when you breathe in and out with maximum effort. Watch this video to learn more about taking a spirometry test.
- Spirometry with bronchodilator tests to measure how much and how fast air moves in and out both before and after you take an inhaled medicine to relax the muscles in your airway.
- Bronchoprovocation tests to measure how your airways react to specific exposures. During this test, you inhale different concentrations of allergens or medicines that may tighten the muscles in your airways. Spirometry is done before and after the test.
- Peak expiratory flow (PEF) tests to measure how fast you can blow air out using maximum effort. This test can be done during spirometry or by breathing into a separate device, such as a tube.
- Fractional exhaled nitric oxide (FeNO) tests to measure levels of nitric oxide in your breath when you breathe out. High levels of nitric oxide may mean that your lungs are inflamed. This test is done in adults and children age 5 and older.
- Allergy skin or blood tests, if you have a history of allergies. These tests can tell your doctor which allergens, such as pet dander or pollen, causes a reaction from your immune system.
Diagnosing asthma in children younger than 6
It can be hard to tell whether a child under age 6 has asthma or another respiratory condition, because young children often cannot perform a pulmonary function test such as spirometry. After checking a child’s history and symptoms, the doctor may try asthma medicines for a few months to see how well a child responds. About 40% of children who wheeze when they get colds or respiratory infections are eventually diagnosed with asthma.
Treatment - Asthma
If you are diagnosed with asthma, your doctor will work with you to create a treatment plan to manage your asthma symptoms and prevent asthma attacks. Treatment usually depends on your age, asthma severity, and response to a given treatment option. Your doctor may adjust your treatment until asthma symptoms are controlled.
Most people are treated long-term with daily controller(s), along with another inhaler for short-term relief, when they have symptoms or to prevent symptoms. An inhaler allows the medicine to go into the mouth and airways.
Watch our video to learn about treatment for asthma.
Short-term relief medicines
Short-term relief medicines, also called quick-relief medicines, help prevent symptoms or relieve symptoms during an asthma attack. They may be the only medicines needed for mild asthma or asthma that happens only with physical activity.
Your doctor will prescribe a quick-relief inhaler for you to carry at all times. Visit the Centers for Disease Control and Prevention (CDC) to learn how to use your asthma inhaler correctly.
Types of short-term relief medicines include:
- Inhaled short-acting beta2-agonists (SABAs) to quickly relax tight muscles around your airways. This allows the airways to open so air can flow through them. Side effects can include tremors and rapid heartbeat. If symptoms and medical history suggest asthma, doctors may treat it with inhaled corticosteroids for a trial period to see whether they help. If symptoms do not improve, corticosteroids will be stopped to avoid side effects.
- Oral and intravenous (IV) corticosteroids to reduce inflammation caused by severe asthma symptoms.
- Short-acting anticholinergics to help open the airways quickly. This medicine may be less effective than SABAs, but it is an option for people who may have side effects from SABAs.
Your doctor may prescribe long-term control medicines to take daily to help prevent symptoms by reducing airway inflammation and preventing narrowing of the airways. Treatment with specific control medicines may differ depending on age, such as whether the person is an adult or child. Return to Causes to review what causes asthma symptoms.
Control medicines include the following.
- Corticosteroids to reduce the body’s inflammatory response. Your doctor may prescribe inhaled or oral (as a pill) corticosteroids. Common side effects from inhaled corticosteroids include a hoarse voice or a mouth infection called thrush. A spacer or holding chamber on your inhaler can help avoid these side effects. Oral corticosteroids can have more side effects than inhaled corticosteroids, because the medicine goes outside the lungs.
- Biologic medicines, such as omalizumab, mepolizumab, reslizumab, and benralizumab, to target specific parts of the body’s response to allergens. Biologic medicines are antibodies used in people who have severe asthma. Benralizumab is injected into a vein, while the other medicines are injected below the skin or in a vein. They are given every few weeks.
- Leukotriene modifiers to reduce inflammation and keep your airways open. You take these pills by mouth, alone or with corticosteroids, depending on what your doctor prescribes.
- Mast cell stabilizers, such as cromolyn, to help prevent airway inflammation when you are exposed to allergens or other triggers. These medicines stop certain immune cells from releasing the signals that cause inflammation.
- Inhaled long-acting bronchodilators, such as long-acting beta2-agonists (LABAs), to keep the airways open by preventing narrowing of the airways. LABAs may be added to your inhaled corticosteroids to reduce narrowing and inflammation. A similar medicine called inhaled long-acting muscarinic antagonists (LAMAs) is sometimes also used.
- Allergy shots, called subcutaneous immunotherapy (SCIT), to reduce the body’s response to allergens. Instead of a shot, the allergens might also be inside a droplet or tablet that you put under your tongue. Rarely, it can cause a life-threatening allergic reaction.
If you have a severe asthma attack and need emergency care, you may be treated with medicines, such as those listed above, given with a nebulizer or IV. You may also receive oxygen therapy or breathing assistance. This may include ventilator support or through a mask with forced air.
In certain cases, your doctor may recommend a procedure called bronchial thermoplasty if you have severe asthma and other treatments are not working. In this procedure, your doctor will enter the airways through the mouth with a bronchoscope. This helps your doctor see inside the airways. Your doctor will then apply heat to the muscles along the airways to make them thinner and help prevent constriction.
Living With - Asthma
After being diagnosed with asthma, work with your doctor to learn how to manage it yourself. Because asthma symptoms may be different at different times, it is important to know which medicines to use to prevent and relieve symptoms. You can work with your doctor to develop a treatment plan, called an asthma action plan. Follow-up care will help to make sure your or your child’s asthma is well-controlled. Staying healthy also includes avoiding asthma triggers and maintaining a healthy lifestyle.
Watch NHLBI’s video Living with and Managing Asthma for more information.
Follow your asthma action plan
Work with your doctor to create an asthma action plan that works for you. An asthma action plan is a written treatment plan document that describes the following.
- How to identify allergens or irritants to avoid
- How to recognize and handle asthma attacks
- Which medicines to take and when to take them
- When to call your doctor or go to the emergency room
- Who to contact in an emergency
If your child has asthma, then your child’s caretakers and school staff should know about the asthma action plan. For a sample plan, see the National Heart, Lung, and Blood Institute’s (NHLBI) Asthma Action Plan.
Your doctor will make sure you are using your inhaler correctly. There are different types of inhalers. Review the way you use your inhaler at every medical visit. Sometimes asthma may get worse because of incorrect inhaler use.
Watch our video on Asthma Action Plans to learn more. Then, download a sample Asthma Action Plan.
Know your asthma triggers
Asthma triggers are things that set off or worsen asthma symptoms. Once you know what these triggers are, you can take steps to control many of them.
Allergens are a common trigger for asthma.
- If animal fur triggers asthma symptoms, keep pets with fur out of your home or bedrooms.
- Keep your house as dust-free and mold-free as possible.
- Remove yourself from what is triggering your symptoms in the workplace. If you have occupational asthma, even low levels of allergen can trigger symptoms.
- Try to limit time outdoors if allergen levels are high.
Other asthma triggers include:
- Emotional stress. Emotional stress, such as intense anger, crying, or laughing, can cause hyperventilation and airway narrowing, triggering an asthma attack.
- Infections, such as influenza (flu). Get the flu vaccine each year to help prevent the flu, which can raise the risk of an asthma attack.
- Medicines. Some people who have severe asthma may be sensitive to medicines, such as aspirin, and may experience serious respiratory problems. Tell your doctor about all medicines you or your child currently takes.
- Poor air quality or very cold air. Pollution or certain kinds of weather, such as thunderstorms, can affect air quality. Pollution can include indoor pollution caused by gases from inefficient cooking or heating devices that are not vented. Outdoor air pollution may be hard to avoid, but you can keep windows closed and avoid strenuous outdoor activity when air quality is low. For guidance, check the National Oceanic and Atmospheric Administration’s Air Quality Forecast Guidance.
- Tobacco smoke, including secondhand smoke.
- Certain foods or food additives (chemicals). This is less common.
Return to Risk Factors to review environments that can trigger asthma.
Receive routine medical care
Regular checkups are important to help your doctor determine how well you are controlling your asthma and adjust treatment if needed. Your doctor will also do regular tests to see how well your lungs are working and how well air is flowing.
Your medicines or dosages may change over time, based on changes in your condition or in your life, such as:
- Age. Older adults may need different treatments because of other conditions they may have and medicines they may take. Beta-blockers, pain relievers, and anti-inflammatory medicines can affect asthma.
- Pregnancy. Your asthma symptoms may change during pregnancy. You are also at higher risk of asthma attacks. Your doctor will continue to treat you with long-term medicines such as inhaled corticosteroids. Controlling your asthma is important for preventing complications such as preeclampsia, pre-term delivery, and low birth weight of the baby.
- Surgery. Asthma may increase your risk of complications during and after surgery. For instance, having a tube put into your throat may cause an asthma attack. Talk to your doctor and surgeon about how to prepare for surgery.
Return to Treatment to review possible treatment options for your asthma.
Manage your asthma at home
Ask your doctor about asthma training or support groups to help you keep asthma under control. Education can help you understand the purpose of your medicines, how to prevent symptoms, how to recognize asthma attacks early, and when to seek medical attention.
As part of your asthma action plan, your doctor may show you how to monitor your asthma using a peak flow meter. You can compare your numbers over time to make sure your asthma is controlled. A low number can help warn you of an asthma attack, even before you notice symptoms.
Keeping a diary may help if you find it hard to follow your asthma action plan or the plan is not working well. If you have any of the following experiences, record them in the diary and make an appointment to see your doctor. Bring the diary with you to your appointment.
- You are limiting normal activities and missing school or work.
- You use your quick-relief inhaler more than two days a week.
- Your asthma medicines do not seem to work well anymore.
- Your peak flow number is low or varies a lot from day to day.
- Your symptoms occur more often, are more severe, or cause you to lose sleep.
If your young child’s asthma is not well-controlled, you may notice that he or she is coughing more at night and eating less. Your child also may seem more tired (called fatigue), irritable, or moody.
Make healthy lifestyle changes
Your doctor may recommend one or more of the following heart-healthy lifestyle changes to help keep asthma symptoms in check.
- Aim for a healthy weight. Obesity can make asthma harder to manage. Talk to your doctor about programs that can help. Even a 5% to 10% weight loss can help symptoms.
- Choose heart-healthy foods. Eating more fruits and vegetables and getting enough vitamin D can provide important health benefits.
- Get regular physical activity. Even though exercise is an asthma trigger for some people, you should not avoid it. Physical activity is an important part of a healthy lifestyle. Talk with your doctor about what level of physical activity is right for you. Ask about medicines that can help you stay active.
- Manage stress. Learn breathing and relaxation techniques, which can help symptoms. Meet with a mental health professional if you have anxiety, depression, or panic attacks.
- Quit smoking or avoid secondhand smoke. Smoking tobacco and inhaling smoke from secondhand smoke make asthma harder to treat. Vaping e-cigarettes and getting exposed to secondhand vapor may also be linked to asthma symptoms. Research suggests that nicotine and flavorings found in vaping e-cigarettes can damage your lungs. Visit Smoking and Your Heart or call the National Cancer Institute’s Smoking Quitline at 1-877-44U-QUIT (1-877-448-7848).
- Try to get good quality sleep. Getting quality sleep can sometimes be difficult with asthma. Develop healthy sleep habits by going to sleep and getting up at regular times, following a calming bedtime routine, and keeping you bedroom cool and dark.
Prevent complications from asthma
Your doctor may recommend that you keep your medicine dose as low as possible to prevent long-term side effects. High doses of certain asthma medicines over time can increase your risk of cataracts and osteoporosis. A cataract is the clouding of lens in your eye. Osteoporosis is a disorder that makes your bones weak and more likely to break. Read more in What People With Asthma Need To Know About Osteoporosis.
Keep your asthma under control and contact your doctor if anything changes. When asthma is unmanaged, it can lead to potentially life-threatening asthma attacks. If you are pregnant, it can put the health of your unborn baby at risk.
Have a plan for asthma attacks
A written asthma action plan developed with your doctor can help you know when to call 9-1-1 for emergency care.
Asthma attacks can be more dangerous for some people. You should seek care immediately during an asthma attack if you or your child:
- Has been hospitalized for asthma in the past year
- Has had life-threatening asthma attacks in the past
- Recently needed oral corticosteroids
- Has not been using inhaled corticosteroids
- Uses more than one canister of inhaled short-acting beta2-agonists (SABAs) medicine each month
- Has a mental health condition or alcohol or drug use disorder
- Does not closely follow your asthma action plan
- Has a food allergy
For young children with asthma, call 9-1-1 if they:
- Seem drowsy, confused, or agitated
- Have a blue tint to the skin and lips
- Have a fast heartbeat
Call your doctor if:
- Your medicines do not relieve an asthma attack
- Your peak flow number is low
Research for Your Health
Improving health with current research
Learn about the following ways the NHLBI continues to translate current research into improved health for people who have asthma. Research on this topic is part of the NHLBI’s broader commitment to advancing scientific discovery for lung disease and health disparities and inequities.
- Advancing the understanding of lung development. The Molecular Atlas of Lung Development Program (LungMAP) integrates many datasets to build a molecular map of the developing lung in both humans and mice. The program helps advance lung research, in part through its web-based data resource, called BREATH, that allows users to access LungMAP data and findings.
- Developing guidelines for the diagnosis and management of asthma. The Expert Panel Report 4 (EPR-4) Working Group was established in 2018 to update the 2007 Guidelines for the Diagnosis and Management of Asthma (EPR-3). The working group members reviewed the latest research to update the guidelines on treatments and management of asthma, including the role of immunotherapy, the effectiveness of indoor allergen reduction, and the use of fractional exhaled nitric oxide (FeNO). View the EPR-4 Summary Report.
- Providing resources for research. The Lung Tissue Research Consortium (LTRC) provides human lung tissues to qualified investigators for use in their research. The program enrolls patients who are planning to have lung surgery, collects blood and other clinical data from these donors, and stores donated tissue that otherwise would be discarded after the lung surgery. The LTRC provides tissue samples and data at no cost to approved investigators.
- Supporting research collaboration. The Pulmonary Trials Cooperative brings together patients, researchers, and healthcare professionals from more than 50 institutions, with a common goal of developing new treatments and testing current clinical care practices.
- The National Asthma Education and Prevention Program (NAEPP). The NAEPP raises awareness about asthma as a major public health problem. Working with medical associations, voluntary health organizations, and community programs, the NAEPP helps to educate patients, healthcare professionals, and the public about asthma.
Advancing research for improved health
In support of our mission, we are committed to advancing asthma research in part through the following ways.
- We perform research. Our Division of Intramural Research and its Pulmonary Branch perform research on asthma.
- We fund research. The research we fund today will help improve our future health. Our Division of Lung Diseases and its Airway Biology and Disease Branch oversee much of the research on asthma we fund, helping us to understand asthma. Our Center for Translation Research and Implementation Science and its Health Inequities and Global Health Branch provide guidance to domestic and global implementation research on heart, lung, and blood, and sleep health disparities, including asthma. Search the NIH RePORTer to learn about research the NHLBI is funding on asthma.
- We stimulate high-impact research. Our Trans-Omics for Precision Medicine (TOPMed) Program includes participants who have asthma, which may help us understand how genes contribute to differences in disease severity and how patients respond to treatment. The NHLBI Strategic Vision highlights ways we may support research over the next decade.
Learn about exciting research areas that the NHLBI is exploring about asthma.
- Exploring new approaches to control asthma symptoms. A study supported by the NHLBI will look at the importance of osteocalcin, a hormone in bone tissue, in causing the constriction of airways in mice that have asthma, to help future treatments. Visit Hormonal Regulation of Airway Diameter by Bone and Its Implication to Asthma to learn more.
- Evaluating how the body’s microbes may affect allergies and asthma. We know that the different bacteria in a person’s body can affect immunity. We support studies to figure out whether different bacteria play a role in development of dust mite allergy-related asthma. Visit Role of the Microbiome in Regulating House Dust Mite-Induced Asthma to learn more.
- Gaining a better understanding of chronic inflammation. Previous studies have shown that epithelial cells, a certain type of cell in the airways, are involved in asthma inflammation. The NHBLI continues to support studies to find specific targets to prevent asthma from worsening. Visit Mechanisms and Consequences of Hyaluronan Production in Asthma to learn more.
- Reducing asthma disparities. The Consortium on Asthma among African-ancestry Populations in the Americas (CAAPA) aims to discover genes that raise asthma risk among people of African ancestry and to study genetic diversity in populations of African descent. Visit New Approaches for Empowering Studies of Asthma in Populations of African Descent to learn more.
Participate in NHLBI Clinical Trials
We lead or sponsor many studies on asthma. See if you or someone you know is eligible to participate in our.
Trials at the NIH Clinical Center
Causes and progression of chronic lung disease
Responses to asthma treatment
Genes involved in development of lung diseases
Asthma sample collections
To learn more about clinical trials at the NIH Clinical Center or to talk to someone about a study that might fit your needs, call the Office of Patient Recruitment 800-411-1222.
Do you have asthma and obesity and live near Aurora, Colorado?
Are you an adult who has asthma and allergies and is willing to undergo brain imaging tests?
Does your child have asthma and an African American or Puerto Rican family background?
Are you a young African American adult who has asthma and lives in or near Detroit?
Are you an adult who has asthma, or are you willing to be a healthy volunteer?
Does your child have asthma and live in or near the Bronx?
Do you have asthma, COPD, or asthma COPD overlap syndrome?
Does your child have asthma and go to public school in Richmond, Virginia?
Do you have asthma and insomnia?
Are you an adult who has asthma, or are you willing to be a healthy volunteer?
Do you live in or near Detroit and have a child who has asthma that is not controlled?
Do you have depression and act as caregiver for a child who has asthma?
Do you have asthma, and are you struggling to reach a healthy weight?
Wondering whether your asthma attack is caused by the common cold or other viruses?
After reading our Asthma Health Topic, you may be interested in additional information found in the following resources.
Related Health Topics
- Asthma Awareness—Learn More Breathe Better Program
- Health Disparities and Inequities
- Learn More Breathe Better
- Lung Diseases
- Lung Tissue Research Consortium (LTRC)
- Multi-Ethnic Study of Atherosclerosis (MESA)
- National Asthma Education and Prevention Program
- National Asthma Education and Prevention Program Resolution on Asthma Management at School
- YouTube: Taking a Spirometry Test