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Asthma Symptoms, Causes, and Medications

  • Reviewed By: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Reviewed on 10/29/2016

What Is Asthma? Definition

A doctor looks at a chest X-ray of a patient with asthma.

Asthma is a chronic lung disorder that can make breathing difficult by narrowing and inflaming the airways (bronchial tubes).

“Asthma” is an ancient Greek word meaning “short breath, panting.” One of the telltale signs of asthma attacks is the wheezing and breathing difficulty that they cause.

Asthma attacks can be a frightening experience, and affect breathing by causing

  • inflammation, swelling, and narrowing of the airways,
  • recurring wheezing,
  • chest tightness,
  • coughing, and
  • shortness of breath.

Chronically inflamed bronchial tubes become very sensitive to inhaled allergens or irritants such as

  • pollen,
  • pollution,
  • tobacco smoke, or
  • triggers such as exercise.

Prevalence of Asthma

About 25 million people in the U.S. have asthma; 7 million of those are children. Asthma reports are on the rise. The condition affects men and women equally. Asthma causes over 14 million visits to doctors each year and nearly 2 million visits to emergency departments.

Asthma Can Be Deadly

Asthma can kill. The rate of asthma deaths spiked from 2,600 in 1979 up to 4,600 in 1988. The reasons for this spike are unknown, but may be related to

  • inadequate medical care,
  • an increased severity of asthma, and/or
  • an increase in the number of people with asthma.

African Americans are about three times as likely to die from asthma as white Americans. Most people who die from asthma are over age 50, but children sometimes die of the condition, too.

Asthma Inhalers & Nebulizers

A young girl uses an inhaler to treat her asthma.

Asthma inhalers and nebulizers have advantages over oral medications and injections in that they deliver medicine directly to the airways. They also have fewer side effects than other forms of asthma medication.

Asthma Inhalers

The most common treatment for asthma involves a device called an inhaler. An inhaler is a small device that delivers asthma medicine directly to the airways. Inhalers come in two types:

  • Metered Dose Inhalers (MDI): MDIs are the most common type of inhaler. They spray medicine from the inhaler like an aerosol can.
  • Dry powder inhalers: Dry powder inhalers deliver a powdered medicine that does not spray from the inhaler. Instead, the user must breathe in the medicine quickly and forcefully.


Sometimes MDIs are used along with a device called a spacer. Spacers help coordinate breathing with the release of the asthma medicine, and also make the droplets of medicine smaller, making it easier to breath them in.


For babies and very young children, an inhaler requires too much work. In that case, a nebulizer can be used. Nebulizers are powered by electricity to turn asthma medicine into a fine mist. The mist is delivered through a tube attached to a facemask or mouthpiece. Disadvantages to nebulizers include the fact that they can be noisy, they can be big, they can be time-consuming, and they may not be very portable.

Asthma Medications for Inhalers & Nebulizers

CCommon medications used with inhalers and nebulizers include the following:

  • Inhaled Corticosteroids: Inhaled corticosteroids reduce inflammation in the airways, which reduces swelling and tightening. Sometimes these medicines are used even without asthma symptoms, as they can help prevent future asthma attacks. Types of inhaled corticosteroids include beclomethasone, budesonide, ciclesonide, flunisolide, fluticasone, and triamcinolone.
  • Short-Acting Bronchodilators: Bronchodilators have no steroids and work by relaxing the tiny muscles that can tighten airways during asthma attacks. Short-acting bronchodilators give quick relief to asthma symptoms. Types of short-acting bronchodilators include albuterol, levalbuterol, terbutaline, and ipratropium.
  • Long-Acting Bronchodilators: Long-acting bronchodilators are taken daily to help control asthma and prevent future asthma attacks. Types of long-acting bronchodilators include salmeterol and formoterol.

The Respiratory System: What Is Respiration?

An illustration shows the bronchiole tubes with normal airway passage.

Respiration is how our bodies allow oxygen in, and also how our bodies releases carbon dioxide.

When we inhale, air passes into our windpipe (trachea), our diaphragm contracts and moves downward creating air space in our chest cavity. The air enters the lungs, passing through the bronchial tubes and finally to the air sacs (alveoli).

Oxygen from the air passes from the alveoli and into the bloodstream through tiny blood vessels called capillaries. Capillaries deliver this oxygen-rich blood to the pulmonary veins, which go to the left side of the heart. The heart then pumps the oxygen-rich blood to the rest of the body.

When you exhale, air that is rich in carbon dioxide (CO2) passes out of your lungs, through the windpipe, and out your nose or mouth.

How Does Asthma Affect Breathing?

The narrowing that occurs in asthma is caused by inflammation, bronchospasm, and hyperreactivity.

When a person has asthma, the airways become inflamed and sensitive. This swelling narrows the airways, making breathing difficult, and often leading to panting and gasping fits. Three factors cause this narrowing and will be discussed in the following slides:

  • Inflammation
  • Bronchospasm
  • Hyperreactivity (Asthma Triggers)

What Causes Asthma? Inflammation

Asthma inflammation causes mucus to fill the bronchiole tubes, resulting in an obstructed airway.

The main cause of narrowing airways in asthma is inflammation, which makes airways more swollen and sensitive. When airways are inflamed, air has a smaller space to pass through. In addition, the muscles surrounding the airways may tighten during an asthma attack, further narrowing the space for airflow.

When airways react to inflammation, they also produce more mucus, which is a sticky and thick liquid substance that can clump together and narrow air passages even further.

Moreover, certain allergy and inflammation cells (eosinophils and white blood cells) accumulate at the site of the inflammation, causing tissue damage and even more narrow airways.

This chain reaction causes the breathing difficulty associated with an asthma attack.

What Causes Asthma? Bronchospasm

An animated illustration shows the muscle constriction of the airways known as bronchospasm.

The lungs are made up of tubes that branch out like a tree. They become smaller and smaller as they enter the lungs, eventually becoming so small that they become microscopic. The larger tubes that split off from the trachea into the lungs are called bronchi.

During an asthma attack, people may experience bronchospasm, where the bronchial tubes tighten and further narrow the airways. Coughing and wheezing may be symptoms of bronchospasm, and bronchospasm can occur when the airways are irritated by cold air.

Bronchospasm can happen suddenly. It can be treated by medicines called bronchodilators.

What Causes Asthma? Asthma Triggers

A smokestack emits greenhouse gases and irritants (left), pollen floats in the air (center) and a woman sneezes due to allergens (right).

People with asthma may become hyperreactive (hypersensitive) to certain inhaled allergens or irritants. These are called triggers, and these triggers can cause even more inflammation and narrowing of the airways.

The reason for this is that some people’s bodies are immunologically inclined to overreact to certain substances. An overactive immune system can set off asthma in this way. But exactly what substance may cause such a reaction varies from person to person. In the next three slides, we’ll review in more detail about asthma triggers.

Which Triggers Cause an Asthma Attack?

Asthma triggers fall into two categories: allergens (specific) and nonallergens – mostly irritants (nonspecific).

Things that can cause an asthma attack are referred to as "triggers." Not everyone with asthma has the same triggers. Triggers can be either allergens or irritants. People with asthma need to learn what their triggers are so the triggers can be managed or avoided altogether.

Recognizing and avoiding your triggers can help you prevent further asthma attacks. Allergists and immunologists are medical doctors who specialize in helping patients identify irritants and allergies that cause problems like asthma. They can help you develop a plan to avoid asthma triggers and feel better more consistently.

Asthma Triggers: Allergens

Wind blowing pollen into the air (top left), a magnified image of a dust mite (top right), a dog and a cat (bottom left), and peanuts (bottom right) are examples of allergens that may cause asthma.

Asthma can have both allergic and nonallergic triggers. Allergic asthma triggers include many allergens. Some of these allergens include

  • pollen,
  • dust,
  • mold,
  • pets,
  • common foods including peanuts, egg, dairy, soy, and fish,
  • sulfites, and
  • latex.

Asthma Triggers: Irritants

A woman suffering from a cold (top left), a bottle of antiinflammatory drugs (top right), cigarette smoke (bottom left) and exterminator spraying for insects in a kitchen (bottom right) are examples of asthma irritants.

Nonallergic asthma triggers include irritants such as:

  • tobacco smoke,
  • viral upper respiratory infections,
  • environmental pollutants such as smog or vehicle fumes,
  • indoor irritants such as perfumes, detergents, and paints,
  • exercise,
  • work-related exposure to chemicals, dusts, and gases,
  • drugs such as aspirin or NSAIDs (nonsteroidal anti-inflammatory drugs), and beta-blockers, and
  • GERD (gastroesophageal reflux disorder).

Asthma Symptoms in Adults and Kids

A mother helps her daughter with an asthma inhaler.

Asthma seems to have both genetic and environmental causes, and can develop at any age. However, asthma does tend to start in children ages 2-6. At this age, asthma is triggered by allergens such as dust mites, tobacco smoke, and viral upper respiratory infections.

Adults can also develop asthma, and only about 30% of adult asthma triggers are related to allergies such as pet dander, mold, or dust mites. Risk factors for adult-onset asthma include being female, obesity, hormonal fluctuations such as those experienced during or after pregnancy or menopause, and viral or other infections.

Types of Asthma: Allergic (Extrinsic)

A young girl with allergic asthma uses her asthma inhaler.

Allergic (extrinsic) asthma is that which is triggered by an allergic reaction. It is an immune system response to an irritant. This is the most common form of asthma, affecting more than half of all sufferers. It can often be managed with medication.

Types of Asthma: Non-Allergic (Intrinsic)

A woman with nonallergic asthma uses an asthma inhaler.

Non-allergic (intrinsic) asthma is caused by factors other than allergies, such as exercise, stress or anxiety, inhaling cold air, smoke, viral infections, and other irritants. This type of asthma is less common, it develops more often in adults, and is more difficult to treat than allergic (extrinsic) asthma.

Symptoms and Signs of Asthma

A man shows symptoms of wheezing, coughing, and chest tightness, signifying an asthma attack.

Symptoms of asthma, both allergic and non-allergic, include

  • shortness of breath,
  • wheezing,
  • coughing, and
  • chest tightness.

Not everyone with asthma will experience all symptoms, and the severity of symptoms can vary depending on the individual—even in an individual they may vary over time.

Asthma: Mild to Severe

Asthma Classification Chart.

The National Asthma Education and Prevention Program classifies asthma based on a patient's symptoms and lung function tests into these four categories:

  • Intermittent
  • Mild persistent
  • Moderate persistent
  • Severe persistent

Acute Asthma Attack

A man uses his asthma inhaler while experiencing an acute asthma attack.

An "asthma attack" is an acute worsening of asthma symptoms. During an acute asthma attack, there is

  • inflammation,
  • bronchospasm, and
  • mucus produced,

leading to symptoms such as

  • difficulty breathing,
  • shortness of breath,
  • wheezing,
  • coughing, and
  • interference with daily activities.

Many times asthma attacks can be controlled with inhalers (inhaled bronchodilators). If that is ineffective, the patient should call 911 or be taken to an emergency room immediately. When asthma does not respond to initial treatment it can result in a life-threatening reaction called status asthmaticus.

Asthma Exams & Tests

A spirometer (left) and peak flow meter (right) are devices that test and measure lung functionality in asthma diagnosis.
  • lung (pulmonary) function tests, including spirometry and or peak flow meter tests, measure lung function,
  • blood tests measure levels of IgE, which are antibodies released during allergic reactions,
  • bronchoprovocation measures how sensitive your airways are,
  • tests to rule out other conditions such as reflux disease or sleep apnea, and
  • chest x-rays or EKGs to find out if a foreign object or another condition is causing your symptoms.

Medical Treatment of Asthma

A bronchodilator or metered-dose inhaler (left) and dry-powder  inhaler (right) may be used in the treatment of asthma.

Asthma medications are classified as either for long-term control, or quick relief. Most are inhaled rather than taken in tablet or liquid form, to act directly on the airways where the breathing problems start.

Long-term control medications include:

  • Inhaled corticosteroids
  • Cromolyn, taken using a nebulizer
  • Omalizumab (anti-IgE), given as an injection
  • Inhaled short-acting beta2-agonists
  • Leukotriene modifiers, taken by mouth
  • Theophylline, taken by mouth

Quick-relief medications include:

  • Inhaled long-acting beta2-agonists

Asthma At A Glance

A boy holds his asthma inhaler.
  • Asthma is a chronic lung disorder that can make breathing difficult. It causes inflammation, swelling, and narrowing of the airways (bronchial tubes).
  • About 25 million people in the U.S have asthma; 7 million of those are children.
  • Asthma involves narrowing of the airways caused by three major factors: inflammation, bronchospasm, and hyperreactivity.
  • Allergy plays a role in some, but not all, asthma patients.
  • Allergens and irritants can cause asthma attacks.
  • Asthma symptoms include shortness of breath,
  • Asthma is diagnosed based physical exam, patient history, and confirmed with breathing tests.
  • The best way to manage asthma is to try to avoid triggers such as allergens or irritants.
  • Medications can reverse or prevent bronchospasm in patients with asthma.

Asthma Symptoms, Causes, and Medications

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