Asthma

Reviewed on 9/26/2022

Things to Know About Asthma

Asthma inflammation causes mucus to fill the bronchiole tubes, resulting in an obstructed airway.
Asthma inflammation causes mucus to fill the bronchiole tubes, resulting in an obstructed airway.
  • Asthma is a disease that affects the breathing passages of the lungs (bronchioles). Asthma is caused by chronic (ongoing, long-term) inflammation of these passages. This makes the breathing tubes, or airways, of the person with asthma highly sensitive to various "triggers.
  • Seek medical care if you are experiencing chest pain or tightness, difficulty breathing, wheezing, or a spasmodic cough that worsens at night.
  • Treatment may incorporate the use of long-term control medications and quick-relief medicines.

When the inflammation is "triggered" by any number of external and internal factors, the walls of the passages swell, and the openings fill with mucus. Muscles within the breathing passages contract (bronchospasm), causing even further narrowing of the airways. This narrowing makes it difficult for air to be breathed out (exhaled) from the lungs. This resistance to exhaling leads to the typical symptoms of an asthma attack.

Because asthma causes resistance, or obstruction, to exhaled air, it is called obstructive lung disease. The medical term for such lung conditions is chronic obstructive pulmonary disease or COPD. COPD is actually a group of diseases that includes not only asthma but also chronic bronchitis and emphysema. Some people with asthma do not have COPD. These are the individuals whose lung function returns to normal when they are not having an attack. Others will have a process of lung airway remodeling from chronic, long-standing inflammation, usually untreated. This results in permanent abnormalities of their lung function with symptoms of obstructive lung disease occurring all the time. These people are categorized as having one of the class of diseases known as COPD.

Can You Get Rid of Asthma?

Like any other chronic disease, asthma is a condition you live with every day of your life. You can have an attack any time you are exposed to one of your asthma triggers. Unlike other chronic obstructive lung diseases, asthma is reversible.

  • Asthma cannot be cured, but it can be controlled.
  • You have a better chance of controlling your asthma if it is diagnosed early and treatment is begun right away.
  • With proper treatment, people with asthma can have fewer and less severe asthma attacks.
  • Without treatment, they will have more frequent and more severe asthma attacks and can even die. Ongoing persistent airway inflammation can lead to progressive deterioration of lung function and can result in disability and even death.

Asthma is on the rise in the United States and other developed countries. We are not sure exactly why this is, but these factors may contribute.

  • We grow up as children with less exposure to infection than did our ancestors, which has made our immune systems more sensitive.
  • We spend more and more time indoors, where we are exposed to indoor allergens such as dust mites and mold.
  • The air we breathe is more polluted than the air most of our ancestors breathed.
  • Our lifestyle has led to our getting less exercise and an epidemic of obesity. There is some evidence to suggest an association between obesity and asthma.

Who Is at Risk for Asthma?

Asthma is a very common disease in the United States, where more than 17 million people are affected. One-third of these are children. Asthma affects all races and is slightly more common in African Americans than in other races.

  • Asthma affects all ages, although it is more common in younger people. The frequency and severity of asthma attacks tend to decrease as a person ages.
  • Asthma is the most common chronic disease in children.

Asthma has many costs to society as well as to the individual affected.

  • Many people are forced to make compromises in their lifestyle to accommodate their disease.
  • Asthma is a major cause of work and school absence and lost productivity.
  • Asthma is one of the most common reasons for emergency department visits and hospitalization.
  • Asthma costs the U.S. economy nearly $13 billion each year.
  • Approximately 5,000 people die of asthma each year in the U.S. These numbers may not take into account those individuals who have developed severe COPD from inadequately treated asthma.

The good news for people with asthma is that you can live your life to the fullest. Current treatments for asthma, if followed closely, allow most people with asthma to limit the number of attacks they have. With the help of your health care provider, you can take control of your care and your life.

What Are the Signs and Symptoms of Asthma Types?

When the breathing passages become irritated or infected, an attack is triggered. The attack may come on suddenly or develop slowly over several days or hours. The main symptoms that signal an attack are as follows:

  1. wheezing,
  2. breathlessness,
  3. chest tightness,
  4. coughing, and
  5. difficulty speaking.

Symptoms may occur during the day or at night. If they happen at night, they may disturb your sleep.

Wheezing is the most common symptom of an asthma attack.

  1. Wheezing is a musical, whistling, or hissing sound with breathing.
  2. Wheezes are most often heard during exhalation, but they can occur during breathing in (inhaling).
  3. Not all asthmatics wheeze, and not all people who wheeze are asthmatics.

Current guidelines for the care of people with asthma include classifying the severity of asthma symptoms, as follows:

  1. Mild intermittent: This includes attacks no more than twice a week and nighttime attacks no more than twice a month. Attacks last no more than a few hours to days. The severity of attacks varies, but there are no symptoms between attacks.
  2. Mild persistent: This includes attacks more than twice a week, but not every day, and nighttime symptoms more than twice a month. Attacks are sometimes severe enough to interrupt regular activities.
  3. Moderate persistent: This includes daily attacks and nighttime symptoms more than once a week. More severe asthma attacks occur at least twice a week and may last for days. Attacks require the daily use of quick-relief (rescue) medication and changes in daily activities.
  4. Severe persistent: This includes frequent severe attacks, continual daytime symptoms, and frequent nighttime symptoms. Symptoms require limits on daily activities.

Just because a person has mild or moderate asthma does not mean that he or she cannot have a severe attack. The severity of asthma can change over time, either for better or for worse.

What Causes Asthma?

The exact cause of asthma is not known.

  • What all people with asthma have in common are chronic airway inflammation and excessive airway sensitivity to various triggers.
  • Research has focused on why some people develop asthma while others do not.
  • Some people are born with the tendency to have asthma, while others are not. Scientists are trying to find the genes that cause this tendency.
  • The environment you live in and the way you live partly determine whether you have asthma attacks.

An asthma attack is a reaction to a trigger. It is similar in many ways to an allergic reaction.

  • An allergic reaction is a response by the body's immune system to an "invader."
  • When the cells of the immune system sense an invader, they set off a series of reactions that help fight off the invader.
  • It is this series of reactions that results in inflammation of the lining of the air passages. This can result in a modification of the cell types lining these airways. More glandular-type cells develop, which can cause the production of mucus. This mucus, along with irritation to muscle receptors in the airways, can cause bronchospasm. These responses cause the symptoms of an asthma attack.
  • In asthma, the "invaders" are the triggers listed below. Triggers vary among individuals.
  • Because asthma is a type of allergic reaction, it is sometimes called reactive airway disease.

Each person with asthma has his or her own unique set of triggers. Most triggers cause attacks in some people with asthma and not in others. Common triggers of asthma attacks include

  • exposure to tobacco smoke or wood smoke;
  • breathing air pollution;
  • inhaling other respiratory irritants such as perfumes or cleaning products;
  • exposure to airway irritants at the workplace;
  • breathing in allergy-causing substances (allergens) such as molds, dust mites, or animal dander;
  • an upper respiratory infection, such as a cold, flu, sinusitis, or bronchitis;
  • exposure to cold air and dry weather;
  • emotional excitement or stress;
  • physical exertion or exercise;
  • reflux of stomach acid known as gastroesophageal reflux disease, or GERD;
  • sulfites, an additive to some foods and wine; and
  • menstruation. (In some, not all, women, asthma symptoms are closely tied to the menstrual cycle.)

Risk factors for developing asthma include

  • hay fever (allergic rhinitis) and other allergies (This is the single biggest risk factor.),
  • eczema (another type of allergy affecting the skin), and
  • genetic predisposition (a parent, brother, or sister also has asthma).

When Should You Call a Doctor for an Asthma Attack?

If you think you or your child may have asthma, make an appointment with your health care provider. Some clues pointing to asthma include the following:

  • wheezing,
  • difficulty breathing,
  • pain or tightness in your chest, and
  • recurrent, spasmodic cough that is worse at night.

If you or your child has asthma, you should have an asthma action plan worked out in advance with your health care provider. This plan should include instructions on what to do when an asthma attack occurs when to call the health care provider, and when to go to a hospital emergency department. The following are general guidelines only. If your provider recommends another plan for you, follow that plan.

  • Take two puffs of an inhaled beta-agonist (a rescue medication), with one minute between puffs. If there is no relief, take an additional puff of inhaled beta-agonist every five minutes. If there is no response after eight puffs, which is 40 minutes, your health care provider should be called.
  • Your provider also should be called if you have an asthma attack when you are already taking oral or inhaled steroids or if your inhaler treatments are not lasting four hours.

Although asthma is a reversible disease, and treatments are available, people can die from a severe asthma attack.

When Should You Go to the Emergency Department for an Asthma Attack?

If you are having an asthma attack and have severe shortness of breath or are unable to reach your doctor in a short period, you must call 911 or go to the nearest hospital emergency department. Do not drive yourself to the hospital. Have a friend or family member drive.

If you are in the emergency room, treatment will be started while the evaluation is still going on.

  • You may be given oxygen through a face mask or a tube that goes in your nose.
  • You may be given aerosolized beta-agonist medications through a face mask or a nebulizer, with or without an anticholinergic agent.
  • Another method of providing inhaled beta-agonists is by using a metered dose inhaler or MDI. An MDI delivers a standard dose of medication per puff. MDIs are often used along with a "spacer" or holding chamber. A dose of six to eight puffs is sprayed into the spacer, which is then inhaled. The advantage of an MDI with a spacer is that it requires little or no assistance from the respiratory therapist.
  • If you are already on steroid medications or have recently stopped taking steroid medications, or if this appears to be a very severe attack, you may be given a dose of IV steroids.
  • If you are taking a methylxanthine, such as theophylline or aminophylline, the blood level of this drug will be checked, and you may be given this medication through an IV.
  • People who respond poorly to inhaled beta-agonists may be given an injection or IV dose of a beta-agonist such as terbutaline or epinephrine.
  • You will be observed for at least several hours while your test results are obtained and evaluated. You will be monitored for signs of improvement or worsening.
  • If you respond well to treatment, you will probably be released from the hospital. Be on the lookout over the next several hours for a return of symptoms. If symptoms should return or worsen, return to the emergency department right away.
  • Your response will likely be monitored by a peak flow meter.

In certain circumstances, you may need to be admitted to the hospital. There you can be watched carefully and treated should your condition worsen. Conditions for hospitalization include the following:

  • an attack that is very severe or does not respond well to treatment;
  • poor lung function observed on spirometry;
  • elevated carbon dioxide or low oxygen levels in your blood;
  • a history of being admitted to the hospital or placed on a ventilator for your asthma attacks;
  • other serious diseases that may jeopardize your recovery; and
  • other serious lung illnesses or injuries, such as pneumonia or pneumothorax (a "collapsed" lung).

What Tests and Procedures Diagnose Asthma?

If you go to the emergency department for an asthma attack, the doctor will first assess how severe the attack is. Attacks are usually classified as mild, moderate, or severe. This assessment is based on several factors:

  • symptom severity and duration,
  • degree of airway obstruction, and
  • the extent to which the attack is interfering with regular activities.

Mild and moderate attacks usually involve the following symptoms, which may come on gradually:

  • chest tightness,
  • coughing or spitting up mucus,
  • restlessness or trouble sleeping, and
  • wheezing.

Severe attacks are less common. They may involve the following symptoms:

  • breathlessness,
  • difficulty talking,
  • tightness in neck muscles,
  • slight gray or a bluish color in your lips and fingernail beds,
  • skin appears "sucked in" around the rib cage, and
  • "silent" chest (no wheezing on inhalation or exhalation).

If you can speak, the health care provider will ask you questions about your symptoms, your medical history, and your medications. Answer as completely as you can. He or she will also examine you and observe you as you breathe.

If this is your first attack or the first time you have sought medical attention for your symptoms, the health care provider will ask questions and perform tests to search for and rule out other causes of the symptoms.

Measurements of how well you are breathing include the following:

  • Spirometer: This device measures how much air you can exhale and how forcefully you can breathe out. The test may be done before and after you take inhaled medication. Spirometry is a good way to monitor your lung function, but this forced maneuver during an attack can worsen your symptoms. This test is a more accurate measurement of your baseline lung function.
  • Peak flow meter: This is another way of measuring how forcefully you can breathe out during an attack. This is a useful tool for monitoring the severity of an attack as well as the adequacy of maintenance therapy. It is a less forceful maneuver and therefore can be used during an attack.
  • Oximetry: A painless probe, called a pulse oximeter, will be placed on your fingertip to measure the amount of oxygen in your bloodstream.

No blood test can pinpoint the cause of asthma.

  • Your blood may be checked for signs of an infection that might be contributing to this attack.
  • In severe attacks, it may be necessary to sample blood from an artery to determine exactly how much oxygen and carbon dioxide are present in your body.

A chest X-ray may also be taken. This is mostly to rule out other conditions that can cause similar symptoms.

If your asthma has just been diagnosed, you may be started on a regimen of medications and monitoring. You will be given two types of medications:

  • Controller/maintenance medications: These are for long-term control of persistent asthma. They help to reduce the inflammation in the lungs that underlies asthma attacks. You take these every day regardless of whether you are having symptoms or not.
  • Rescue medications: These are for short-term control of asthma attacks. You take these only when you are having symptoms or are more likely to have an attack -- for example when you have an infection in your respiratory tract. Some feel that the term rescue medication means that you only use it in an emergency. These medications should be used for any asthma symptoms, like cough, wheezing, chest tightness, or shortness of breath. They can also be used in anticipation of an activity that causes shortness of breath. It is important to keep track of the frequency that these inhalers are used for unplanned symptoms (that is, not when used in anticipation of symptoms for an activity). Asthma is considered well-controlled when rescue therapy is used less than five times per week. If asthma is not well controlled, then your provider can add additional medications. This concept is important because it helps in overall control and patient understanding of their asthma management. As is described below, medication can be added (step-up therapy) when rescue inhaler use increases for a while. Similarly, medications can be reduced (step-down therapy) when rescue use is minimum or nonexistent.

Your treatment plan will also include other components:

  • awareness of your triggers and avoiding the triggers as much as possible;
  • recommendations for coping with asthma in your daily life;
  • regular follow-up visits to your health care provider; and
  • use of a peak flow meter.

At your follow-up visits, your health care provider will review how you have been doing.

  • He or she will ask you about the frequency and severity of attacks, the use of rescue medications, and peak flow measurements.
  • Lung function tests may be done to see how your lungs are responding to your treatment.
  • This is a good time to discuss medication side effects or any problems you are having with your treatment.

The peak flow meter is a simple, inexpensive device that measures how forcefully you can exhale.

  • Ask your healthcare provider or an assistant to show you how to use the peak flow meter. He or she should watch you use it until you can do it correctly.
  • Keep one in your home and use it regularly. Your health care provider will make suggestions as to when you should measure your peak flow.
  • Checking your peak flow is a good way to help you and your health care provider assess what triggers your asthma and its severity.
  • Check your peak flow regularly and keep a record of the results. Over time, your health care provider may be able to use this record to determine appropriate medications and reduce the dose or side effects.
  • Peak flow measures fall just before an asthma attack. If you use your peak flow meter regularly, you may be able to predict when you are going to have an attack.
  • It can also be used to check your response to rescue medications.

Together, you and your health care provider will develop an action plan for you in case of an asthma attack. The asthma action plan will include the following:

  • how to use the controller medication;
  • how to use rescue medication in case of an attack;
  • what to do if the rescue medication does not work right away;
  • when to call the health care provider; and
  • when to go directly to the hospital emergency department.

How Is Asthma Treated?

Since asthma is a chronic disease, treatment goes on for a very long time. Some people have to stay in treatment for the rest of their lives. The best way to improve your condition and live your life on your terms is to learn all you can about your asthma and what you can do to make it better.

  • Become a partner with your health care provider and his or her support staff. Use the resources they can offer -- information, education, and expertise -- to help yourself.
  • Become aware of your asthma triggers and do what you can to avoid them.
  • Follow the treatment recommendations of your health care provider. Understand your treatment. Know what each drug does and how it is used.
  • See your health care provider as scheduled.
  • Report any changes or worsening of your symptoms promptly.
  • Report any side effects you are having with your medications.

These are the goals of treatment:

  • Prevent ongoing and bothersome symptoms;
  • Prevent asthma attacks;
  • Prevent attacks severe enough to require a visit to your provider or an emergency department or hospitalization;
  • Carry on with normal activities;
  • Maintain normal or near-normal lung function; and
  • Have as few side effects of medication as possible.

If you have been treated in a hospital emergency department, you will be discharged once you respond well to the treatment. You may be asked to see your primary care provider or an asthma specialist (allergist or pulmonologist) in the next day or two.

If your symptoms return, or if you begin to feel worse, you should immediately contact your health care provider or return to the emergency department.

  • Take your prescribed medications as directed, both controller and rescue medications.
  • See your health care provider regularly according to the recommended schedule.
  • Avoid any known triggers.
  • If you smoke, quit.

If you follow the asthma treatment guidelines, you can help minimize the frequency and severity of your asthma attacks.

  • Asthma is now treated with a step-wise approach.
  • Intermittent asthma is treated with a rescue inhaler which is only used for symptoms.
  • Persistent asthma requires the use of maintenance medication, usually initially an inhaled steroid, but other medications such as leukotriene inhibitors are also used. The more severe the asthmatic condition, the more maintenance medications are required, and therapy is "stepped up." These additional medications include long-acting beta-agonists, oral steroids, and in some cases, theophyllines or omalizumab.
  • As asthma improves, decreasing the amount of medication (under a physician's guidance) and in some cases, stopping some of the medication may be indicated. This is referred to as "stepping down" therapy.

What Home Remedies Treat Asthma?

Current treatment regimens are designed to minimize discomfort, inconvenience, and the extent to which you have to limit your activities. If you follow your treatment plan closely, you should be able to avoid or reduce your visits to your health care provider or the emergency department.

  • Know your triggers and do what you can to avoid them.
  • If you smoke, quit.
  • Do not take cough medicine. These medicines do not help asthma and may cause unwanted side effects.
  • Aspirin and nonsteroidal anti-inflammatory drugs, such as ibuprofen, can cause asthma to worsen in certain individuals. These medications should not be taken without the advice of your health care provider.
  • Do not use nonprescription inhalers. These contain very short-acting drugs that may not last long enough to relieve an asthma attack and may cause unwanted side effects.
  • Take only the medications your health care provider has prescribed for your asthma. Take them as directed.
  • Do not take any nonprescription preparations, herbs, or dietary supplements, even if they are completely "natural," without talking to your healthcare provider first. Some of these may have unwanted side effects or interfere with your medications.
  • If the medication is not working, do not take more than you have been directed to take. Overusing asthma medications can be dangerous.
  • Be prepared to go on to the next step of your action plan if necessary.

If you think your medication is not working, let your healthcare provider know right away.

What Medications Are Used for the Treatment of Asthma Attacks?

Controller medicines help minimize the inflammation that causes an acute asthma attack.

  • Long-acting beta-agonists (LABA): This class of drugs is chemically related to adrenaline, a hormone produced by the adrenal glands. Inhaled long-acting beta-agonists work to keep breathing passages open for 12 hours or longer. They relax the muscles of the breathing passages, dilating the passages and decreasing the resistance to exhaled airflow, making it easier to breathe. They may also help to reduce inflammation, but they have no effect on the underlying cause of the asthma attack. Side effects include rapid heartbeat and shakiness. Salmeterol (Serevent), formoterol (Foradil), indacaterol (Arcapta), and vilanterol (used in Breo and Anoro) are long-acting beta-agonists. These drugs should not be used alone in patients with asthma. There is a boxed warning based on the SMART trial with salmeterol in which there was an increased risk of cardiac death in asthmatics. This issue appears to be mitigated when these drugs are used in combination with inhaled steroids.
  • Inhaled corticosteroids are the main class of medications in this group. The inhaled steroids act locally by concentrating their effects directly within the breathing passages, with very few side effects outside of the lungs. Beclomethasone (Beclovent), fluticasone (Flovent, Arnuity), budesonide (Pulmicort), and triamcinolone (Azmacort) are examples of inhaled corticosteroids.
  • Combination therapy with both a LABA and an inhaled corticosteroid: These include Advair (salmeterol, fluticasone), Symbicort (formoterol, budesonide), and Dulera (formoterol, mometasone), and are all taken twice daily. Newer agents like Breo are combination therapies that only need to be taken once daily.
  • Leukotriene inhibitors are another group of controller medications. Leukotrienes are powerful chemical substances that promote the inflammatory response seen during an acute asthma attack. By blocking these chemicals, leukotriene inhibitors reduce inflammation. The leukotriene inhibitors are considered the second line of defense against asthma and usually are used for asthma that is not severe enough to require oral corticosteroids.
  • Zileuton (Zyflo), zafirlukast (Accolate), and montelukast (Singulair) are examples of leukotriene inhibitors.
  • Methylxanthines are another group of controller medications useful in the treatment of asthma. This group of medications is chemically related to caffeine. Methylxanthines work as long-acting bronchodilators. At one time, methylxanthines were commonly used to treat asthma. Today, because of significant caffeine-like side effects, they are being used less frequently in the routine management of asthma. Theophylline and aminophylline are examples of methylxanthine medications.
  • Cromolyn sodium is another medication that can prevent the release of chemicals that cause asthma-related inflammation. This drug is especially useful for people who develop asthma attacks in response to certain types of allergic exposures. When taken regularly prior to exposure, cromolyn sodium can prevent the development of an asthma attack. However, this medicine is of no use once an asthma attack has begun.
  • Omalizumab belongs to a newer class of agents that works with the body's immune system. In people with asthma who have an elevated level of Immunoglobulin E (IgE), an allergy antibody, this drug given by injection may be helpful with symptoms that are more difficult to control. This agent inhibits IgE binding to cells that release chemicals that worsen asthma symptoms. This binding prevents the release of these mediators, thereby helping in controlling the disease.

Rescue medications are taken after an asthma attack has already begun. These do not take the place of controller drugs. Do not stop taking your controller drug(s) during an asthma attack.

  • Short-acting beta-agonists (SABA) are the most commonly used rescue medications. Inhaled short-acting beta-agonists work rapidly, within minutes, to open the breathing passages, and the effects usually last four hours. Albuterol (Proventil, Ventolin) is the most frequently used SABA medication.
  • Anticholinergics are another class of drugs useful as rescue medications during asthma attacks. Inhaled anticholinergic drugs open the breathing passages, similar to the action of beta-agonists. Inhaled anticholinergics take slightly longer than beta-agonists to achieve their effect, but they last longer than beta-agonists. An anticholinergic drug is often used together with a beta-agonist drug to produce a greater effect than either drug can achieve by itself. Ipratropium bromide (Atrovent) is the inhaled anticholinergic drug currently used as a rescue asthma medicine.

Can Asthma be Cured?

Most people with asthma are able to control their condition if they work together with a health care provider and follow their treatment regimen carefully.

People who do not seek medical care or do not follow an appropriate treatment plan are likely to experience worsening of their asthma and deterioration in their ability to function normally.

Can You Prevent Asthma?

You need to know how to prevent or minimize future asthma attacks.

  • If your asthma attacks are triggered by an allergic reaction, avoid your triggers as much as possible.
  • Keep taking your asthma medicines after you are discharged. This is extremely important. Although the symptoms of an acute asthma attack go away after appropriate treatment, asthma itself never goes away.

Where Can You Get Information about Asthma Support Groups and Counseling?

Allergy & Asthma Network Mothers of Asthmatics
2751 Prosperity Avenue, Suite 150
Fairfax, VA 22031
(800) 878-4403

American Lung Association
61 Broadway, 6th Floor
New York, NY 10006
(212) 315-8700

Asthma and Allergy Foundation of America
1233 20th St NW, Suite 402
Washington, DC 20636
(202) 466-7643

What Does Asthma Treatment Look Like (Pictures)?

A child with asthma using a metered dose inhaler.
A child with asthma uses a metered-dose inhaler.

An adult with asthma using a spirometer to measure how forcefully she can exhale.
An adult with asthma uses a spirometer to measure how forcefully she can exhale.

A pulse oximeter measures the amount of oxygen in your bloodstream.
A pulse oximeter measures the amount of oxygen in your bloodstream.

A person with asthma receives an inhalation treatment using a hand-held nebulizer.
A person with asthma receives an inhalation treatment using a handheld nebulizer.

A child with asthma uses a metered dose inhaler with a spacer.
A child with asthma uses a metered-dose inhaler with a spacer.

6 Signs and Symptoms of Asthma Attacks and Triggers in Children

Signs and symptoms of an asthma attack and triggers in children include:

  1. Mild, moderate, or severe wheezing
  2. Cough
  3. Chest tightness
  4. Bronchitis
  5. Pneumonia
  6. Exercise
Reviewed on 9/26/2022
References
Akhter, Javeed. "Can asthma be cured? What are the latest treatments?" Nov. 21, 2018. <https://www.scientificamerican.com/article/can-asthma-be-cured-what/>.

Fanta, C. "Asthma."NEJM 360 (2009): 1002-1014.