- What Is Asthma?
- What Causes Asthma?
- Who Gets Asthma?
- What Is an Asthma Attack Like?
- What Is the Difference Between Allergies and Asthma?
- What Are the Effects of Asthma?
- When Should Someone Seek Medical Care for Asthma?
- Can Asthma Be Cured?
- What Are Medications for Asthma?
- Can Asthma Attacks Be Prevented?
- For More Information
- Asthma FAQ Topic Guide
What Is Asthma?
When an exacerbation or "attack" of asthma takes place, the inflammation in the airways causes the lining of the breathing passages to swell. This swelling narrows the diameter of the airway, eventually to a point where it is hard to exchange enough air to breathe comfortably. This is when coughing, wheezing, and the sensation of distress start.
Asthma can have varying intensity of symptoms that are characterized as follows:
- Mild intermittent: Symptoms are less than or equal to two per week and less than or equal to two nighttime awakenings per month. The attacks don't last long, and they are alleviated quickly with medication. There are no symptoms between attacks.
- Mild persistent: Symptoms are greater than two per week but less than one per day and more than two nighttime attacks per month. These worsening symptoms or exacerbations may affect activity.
- Moderate persistent: Daily symptoms include more than one nighttime attack per week. These patients require daily use of short-acting bronchodilators (rescue medication). Exacerbations do affect activity.
- Severe persistent: Continual symptoms result in limited physical activity with frequent nighttime attacks.
There are also several types of asthma.
- Adult-onset asthma develops after age 20. It is less common than asthma in children, and it affects more women than men.
- Exercise-induced asthma involves symptoms that occur about five to 20 minutes after beginning an exercise that involves breathing through the mouth. Sports and games that require continuous activity or that are played in cold weather (for example, long-distance running, hockey, soccer, and cross-country skiing) are the most likely to trigger an asthma attack. Other physical exertions that can trigger an attack include laughing, crying, and hyperventilating. Any activity or environment that dries or cools the airway can result in bronchospasm and symptoms may result (cough, shortness of breath, and chest tightness).
- Occupational asthma occurs in response to a trigger in the workplace. These triggers include contaminants and allergens in the air and extremes of temperature or humidity.
- Nocturnal asthma occurs between midnight and 8 a.m. It is triggered by allergens in the home such as dust and pet dander or is caused by sinus conditions. It is also affected by the natural daily rhythm (circadian clock) of the body's steroid (cortisol) output, which tends to be at the lowest levels in the early morning hours.
What Causes Asthma?
While there is no known specific cause of asthma, what all people with asthma have in common is chronic airway inflammation. Their airways are highly sensitive to various triggers. When their airways come into contact with a trigger, the airways become inflamed (they fill with mucus, swell, and narrow). Then muscles within the airways contract, causing even further narrowing of the airways. This makes breathing difficult and results in an asthma attack.
Triggers are different for different individuals. Common ones include the following:
- Exposure to tobacco smoke
- Breathing polluted air
- Inhaling irritants such as perfume and cleaning products
- Allergens such as molds, dust, and animal dander
- Exposure to cold, dry weather
- Exercise or physical exertion
- Medications including aspirin and nonsteroidal antiinflammatory drugs, such as ibuprofen
- An upper respiratory infection such as a cold, flu, or bronchitis
- Sulfites (additives to some foods and wines)
Changes in weather can also trigger asthma attacks because of the irritants and allergens stirred up by wind and rain.
Asthma is on the rise in the United States and other developed countries. While the reasons are not clear, the following factors may contribute to the rise:
- Spending more time indoors where exposure to indoor allergens such as dust and mold and some chemicals from building materials is greater
- Living in cleaner conditions than people did in the past, which makes our immune systems more sensitive (reactive) to triggers
- Exposure to increased air pollution
- Increased physical inactivity (lack of exercise)
Who Gets Asthma?
Asthma affects millions of people worldwide. The number of people affected is eight to 10 times higher in industrialized countries than in developing ones.
Children age 10 and younger account for half of asthma cases. In most children, asthma develops before they are 5 years of age, and in more than half, asthma develops before they are 3 years of age.
More than twice as many boys than girls have asthma, although boys are more likely to experience a decrease in symptoms as they reach adolescence. In adult-onset asthma, the number is reversed. Twice as many women than men visit the emergency department and are admitted to the hospital with asthma.
Asthma affects all races worldwide but is more common in blacks and Hispanics, but this may be due to socioeconomic conditions rather than genetics.
Occupational asthma (asthma triggered at work by exposure to irritants present at the workplace) is most common in those who work with animals or animal-derived products and in industries such as plastics, rubber, chemical, textile, electronics, painting, printing, metalworking, baking, and gardening.
Risk factors for asthma include the following:
- Smoking or living with a smoker is a major risk factor. A significant percentage of children who have asthma have at least one parent who smokes.
- A family history of asthma: If one parent has asthma, a person has a 25% chance of developing it. If both parents have it, a person has a 50% chance of manifesting asthma.
- Having allergies, including hay fever and eczema: It is not known why some people have allergies and some don't, but allergies can be inherited (although people don't necessarily develop the same allergies as their parents have).
- Having allergies or severe viral infections before the age of 3
- Living in the inner city, especially in a low-income group
- Being exposed to mice and cockroach waste products
- Frequently being exposed to triggers
What Is an Asthma Attack Like?
People with asthma react in different ways to risk factors and triggers. Some experience asthma symptoms when they are exposed to several factors or triggers at once, while for others, exposure to one trigger alone is enough to set off an attack. Some people have more severe attacks when they are exposed to more than one trigger.
When people with asthma are exposed to their triggers, their immune systems start trying to fight off the allergens. This results in inflammation (swelling) of the walls or lining of the air passages that blocks or narrows the airways. This makes breathing difficult (like breathing through a straw for a long time) and noisy, and/or it causes coughing.
When breathing passages become irritated or infected, an asthma attack is triggered. Asthma attacks do not always occur immediately after someone is exposed to a trigger. Depending on the person and the particular trigger, an attack can happen hours or even days later. It may occur during either the day or night.
The main asthma symptom is wheezing. Wheezing is a whistling, hissing sound when breathing. This noise is made by the sound of air passing through narrowed tubes (air passages). Wheezes can occur during inhaling or exhaling but are usually heard while exhaling.
What Is the Difference Between Allergies and Asthma?
Allergies and asthma are different, though they may have related reactions and some of the body's chemicals that are involved in allergies are also involved in asthma. An allergy is an inflammatory reaction or response to a specific substance. Allergic reactions can involve nasal membranes, the eyes, the skin, the tongue, and the breathing passages in severe reactions. Allergy symptoms include an itchy, stuffy, or runny nose, sneezing, itchy, red, or irritated skin, and itchy, burning, or watery eyes.
Asthma is a chronic inflammatory lung (lower respiratory) disease that causes difficulty breathing.
The things that trigger allergies can also trigger asthma attacks. Allergy symptoms may be a sign of irritants in the air that can provoke asthma symptoms, and allergy attacks can lead to asthma attacks. With both allergies and asthma, people's immune systems react to fight off the allergens (the material that sets off the reaction). The resulting inflammation causes the airways in people with asthma to become significantly narrowed. The swelling that is called inflammation comes from increased mucus and an increased number of white blood cells in the walls of the air passages. In addition, the air passages are narrowed by the contraction of the muscle that surrounds the lining of the airways. These irritated muscles contract in excess, like a rubber band that closes the air tubes even further.
What Are the Effects of Asthma?
- Five thousand people die each year from asthma.
- Each year, asthma is responsible for 1.5 million emergency department visits, 500,000 hospital admissions, and 100 million days of restricted activity.
- In lost work and productivity, asthma is responsible for approximately $13 billion each year.
- Asthma accounts for more school absences and more hospitalizations of children than any other chronic illness.
When Should Someone Seek Medical Care for Asthma?
If someone has had symptoms of asthma, talking with a doctor is important. A doctor will ask questions about that person's symptoms, medical history, and medications.
The doctor will also perform breathing tests or blood tests to search for and rule out other causes of the symptoms (not all wheezing is asthma). A chest X-ray may also be taken to rule out other conditions that can cause similar symptoms.
If a person does have asthma, he or she will need to work out an action plan with the doctor in order to be prepared for an asthma attack.
Anyone who feels acutely short of breath or feels that he or she may be in respiratory distress should immediately seek care in an emergency department. This is also true for people with asthma who feel their symptoms are worse than usual or are not responding to usual treatment.
Can Asthma Be Cured?
Asthma symptoms and attacks can improve with treatment or with time, but asthma as a disease is not curable. Treatment can go on for a long time, and some people have to use medication for the rest of their lives.
Approximately half of children diagnosed with asthma outgrow their disease by late adolescence or early adulthood and require no further treatment. In some of these individuals, however, exposure to major respiratory irritants (such as smoking, massive exposure to fumes, etc.) later in life may trigger asthma symptoms once again.
Patients who do not control their asthma usually develop more severe asthma over time. More importantly, the chronic airway inflammation that can be found in asthma when left unchecked can result in permanent airway damage. This damage can cause patients to develop chronic obstructive pulmonary disease (COPD). In fact, the most common cause for the development of COPD in nonsmokers is asthma.
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What Are Medications for Asthma?
There are two types of asthma medications.
- Controller medications are for long-term control of persistent asthma. They help reduce the inflammation in the lungs that is behind asthma attacks. Controller medications should be taken every day whether someone is having symptoms or not. Controller medications include inhaled corticosteroids (the main type of medication), leukotriene inhibitors, methylxanthines, and cromolyn sodium.
- Rescue medications are taken after an asthma attack has begun. They stop the attack. Rescue medications include beta-agonists and anticholinergics, as well as systemic (pills or injectable) corticosteroids.
Knowing which medication is which is very important because a controller medication will not give immediate relief if someone is having an asthma attack.
Controller medications should not be stopped just because a person feels fine and has not had an asthma attack for a while. Feeling fine usually means that the controller is working to keep airways free from inflammation. Also, if a controller medication is stopped and a person starts experiencing asthma symptoms again, those symptoms are harder to control. If the controller medication seems to have stopped symptoms, a person can talk to his or her doctor about changing the dose or medication.
Talking with a doctor about possible side effects is important.
For some people, allergy shots can help control asthma symptoms.
For more complete information on medications, visit Understanding Asthma Medications.
For both controller and rescue inhaler medications to be effective, they need to be properly administered so that the medication can reach the deeper parts of the lungs where they are needed. It is important to receive teaching from a health-care provider in the correct use of handheld inhaler devices.
Can Asthma Attacks Be Prevented?
While asthma attacks may not always be able to be prevented, asthma can be managed.
- Avoiding triggers as much as possible is the best way to prevent asthma attacks (for example, eliminating pollen, dust, and mold from a home).
- Exposure to pets when children are very young may lower the risk of developing asthma. Children who live with two or more pets are less likely to react to allergens. If, however, an individual is already allergic to pets, it may be important to avoid exposure to that particular trigger.
- Taking medications as directed is essential.
- People who have outdoor allergies should avoid outside activities when the pollen count or pollution index is high.
- For exercise-induced asthma, several things can help. Spending time warming up before starting strenuous activity and gradually cooling down afterward, avoiding activity during a respiratory tract infection, and avoiding exertion in extremely cold weather may help prevent an asthma attack.
- Yoga may help manage asthma. Sahaja yoga is a type of meditation based on yoga principles that was found to be somewhat effective in managing moderate to severe asthma. Other forms of relaxation training, mediation, and stress reduction may also be of benefit.
For More Information
American College of Allergy, Asthma & Immunology
85 West Algonquin Road, Suite 550
Arlington Heights, IL 60005
American Academy of Asthma, Allergy, and Immunology
611 East Wells Street
Milwaukee, WI 53202
American Lung Association
61 Broadway, 6th floor
New York, NY 10006
Asthma & Allergy Foundation of America
1233 20th Street NW
Washington, DC 20036
Asthma Society of Canada
130 Bridgeland Avenue, Suite 425
Toronto, Ontario M6A 1Z4
Centers for Disease Control and Prevention/
National Center for Environmental Health
National Institute of Allergy and Infectious Diseases
6610 Rockledge Drive, MSC 6612
Bethesda, MD 20892
National Heart Lung and Blood Institute
PO Box 30105
Bethesda, MD 20824