What causes asthma?
During an asthma attack, the smooth muscle layer goes into spasm, narrowing the airway. The middle layer swells because of inflammation, and more mucus is produced. In some segments of the airway, the mucus forms clumps that nearly or completely block the airway. These clumps are called mucus plugs. In most cases, asthma is caused by inhaling an
allergen that sets off the chain of biochemical and tissue changes leading to airway inflammation, bronchoconstriction, and wheezing. Because avoiding (or at least minimizing) exposure is the most effective way of treating asthma, it is vital to identify which allergen or irritant is causing symptoms in a particular patient.
In an asthma attack, the smooth muscles of the bronchi narrow (called bronchoconstriction), and the tissues lining the airways swell from inflammation and secrete mucus into the airways. The top layer of the lining of the airways can become damaged and shed cells. These actions further narrow the diameter of the airways; the narrowing requires the person to exert more effort to move air in and out of the lungs. In asthma, airway obstruction is reversible, meaning that with appropriate treatment or on their own, the muscular contractions of the airways stop, the airway obstruction ends, and the airflow into and out of the lungs returns to normal. This damage results in the development of easily irritated bronchial tubes, which is called hyper-responsiveness. This condition is then causes the lungs to become excessively "twitchy" and to react (or overreact) to previously non-allergic stimuli, such as cold weather, pollution, dry air, and chemical odors. The also-twitchy bronchial tubes will react by going into spasm, which leads to the symptoms of shortness of breath, coughing, wheezing, and chest tightness. This entire process is possibly reversible if caught early in its onset by establishing preventive measures or treating with appropriate medication.
In a person who has asthma, the airways narrow in response to stimuli that usually do not affect the airways in normal lungs. The narrowing can be triggered by many inhaled allergens, such as pollens, particles from dust mites, body secretions from cockroaches, particles from feathers, and animal dander. These allergens combine with immunoglobulin E (a type of antibody) on the surface of mast cells to trigger the release of asthma-causing chemicals from these cells. (This type of asthma is called allergic asthma.) Although food allergies induce asthma only rarely, certain foods (such as shellfish and peanuts) can induce severe attacks in people who are sensitive to these foods.
The symptoms of asthma occur when some trigger causes the lung’s airways to swell and produce excess mucus. The smooth muscles that line the airways (called bronchioles) contract, narrowing the airways and making it difficult to breathe. The most common triggers are substances to which the child is allergic, such as household dusts or molds, animal dander, or pollen. Triggers can also be irritants, such as perfumes, aerosol sprays, air pollution, or cigarette smoke. Some children have asthma attacks when exposed to cold air, during times of stress, or when they engage in physical exercise. Upper respiratory infections can also trigger an asthma attack.
Inflammation is our body's response to foreign or toxic substances that enter or come in contact with the body. Inflammation is caused by the arrival of blood and protective cells into the area involved. When a bacterial infection occurs somewhere in our body, white blood cells blood rush to the infected site and try to either destroy the bacteria or isolate and neutralize their harmful effects. Inflammation causes mucus to build up in these tubes, cutting down on the space available to move air. Inflammation also stimulates the muscles around these tubes to contract, narrowing the tubes and further cutting down the airflow. Although inflammation is the root of all asthma, the trigger for this inflammation is different for different people. Inflammation is an important part of your body's response to injury or infection. Basically, inflammation is the immune system's call to action. Signals sent by the immune system recruit an army of cells to fight off invaders, such as bacteria or viruses. They also start the healing process when there are signs of tissue damage.
In people with asthma, the lungs and airways overreact to foreign substances in the air, such as cat hair, mold or pollution. Sometimes even clean, cold air can constrict the airways, especially in people with exercise-induced asthma. In many ways, asthma is a type of allergic reaction, which is why many people with asthma also see an allergy specialist to help manage their condition.
More information on asthma
What is asthma? - Asthma is a chronic inflammatory respiratory disease characterized by periodic attacks of wheezing, shortness of breath, and a tight feeling in the chest.
What types of asthma are there? - Types of asthma include child-onset asthma, adult-onset asthma, exercise-induced asthma, cough-variant asthma, occupational asthma, nocturnal asthma.
What's bronchial asthma? - Bronchial asthma is a disease of the lungs in which an obstructive ventilation disturbance of the respiratory passages evokes a feeling of shortness of breath.
What is exercise-induced asthma? - Exercise-induced asthma is a form of asthma that some people have during or after physical activity. Exercise-induced asthma is common.
What is adult-onset asthma? - Adult onset asthma generally is the onset of asthma for the first time in someone of middle age or older. Adult-onset asthma develops after age 20.
What is status asthmaticus? - Status asthmaticus is a severe asthma episode that does not respond to standard treatment. Status asthmaticus is caused by severe bronchospasm.
What causes asthma? - Asthma is caused by inhaling an allergen that sets off the chain of biochemical and tissue changes leading to airway inflammation, bronchoconstriction, and wheezing.
What're the asthma triggers? - Many risk factors have been linked to triggering asthma attacks. There are two basic types of asthma triggers, allergic triggers, non-allergic triggers.
Asthma and allergy - Asthma attacks (worsening of asthma symptoms) can be triggered by allergies. Allergy is the leading cause of asthma.
What is an asthma attack? - An asthma attack occurs when the small and medium-sized airways become inflamed and constricted after being exposed to a trigger.
Asthma in children - Asthma is the most common chronic condition of childhood. Asthma symptoms can interfere with many school activities for children.
Asthma and pregnancy - During pregnancy, asthma or asthma episodes will become worse for an estimated one-third of pregnant women, particularly women who have severe asthma.
Asthma in adults and older people - Identifying asthma in the elderly can be difficult because asthma symptoms can be confused with symptoms of heart or lung diseases.
What're the complications of asthma? - Uncontrolled asthma in pregnant women puts them at higher risk for complications that can include early labor, hypertension, gestational diabetes.
What are the symptoms of asthma? - The symptoms of asthma include labored breathing, constriction of the chest, coughing and gasping usually brought on by allergies.
What're the warning signs of asthma? - Most people with asthma have warning signs before symptoms appear. There are many warning signs of an asthma episode.
How is asthma diagnosed? - The diagnosis of asthma is made on the basis of typical symptoms and signs. Positive allergy tests support a diagnosis of asthma.
What're the treatments for asthma? - Treatment of asthma is aimed at avoiding known allergens and respiratory irritants and controlling symptoms and airway inflammation through medication.
What quick relief (rescue) medications cure asthma? - Short-acting beta-agonists are the most commonly used asthma rescue medications. Anticholinergics are another class of asthma drugs.
Long-term asthma control medications - Combinations of steroids and other medications are effective for both treating and preventing asthma attacks in patients with moderate to severe asthma.
What're asthma inhalers? - Most asthma drugs are inhaled using special devices or nebulizers. Two common types include dry powder asthma inhalers and metered-dose asthma inhalers.
What're asthma nebulizers? - Asthma nebulizers can be used with all classes of inhaled medications but are most commonly used with short-acting beta2 agonists and ipratropium bromide.
How to control acute asthma attacks? - Acute asthma is an acute exacerbation of wheezing, unresponsive to usually effective therapy and necessitating care in an emergency room or hospital ward.
How to manage chronic asthma symptoms? - The aims of management are to recognize asthma, to abolish symptoms, to restore normal or best possible long term airway function.
What asthma relievers are available? - Asthma reliever is a drug that provides relief from asthma symptoms and is the most commonly used asthma medication.
What asthma preventers are available? - Asthma preventers are to be used twice a day regardless of whether your child has symptoms of asthma.
What's the treatment for childhood asthma? - The goals of asthma therapy are to prevent child from having chronic and troublesome symptoms, to maintain child's lung function.
What's the treatment for asthma in the elderly? - Diagnosis and treatment of asthma can be more complicated in people age 65 and older than in those who are younger.
What can be done to prevent asthma? - Avoiding known allergens and respiratory irritants can reduce asthma symptoms. People with asthma should minimize risk for respiratory tract infections.