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Asthma is a disease of the bronchial tubes, or airways, of the lungs that makes breathing difficult. Symptoms include frequent coughing-especially at night, shortness of breath, wheezing, and chest tightness, pain, or pressure. Asthma attacks can be triggered by infections such as colds or the flu, exercise, cold weather, tobacco smoke, air pollution, allergens, and chemical odors.

Asthma is one of the most common chronic diseases. About one third of those affected are children under age 18. Asthma may occur at any age, although a first attack is more likely to occur before the age of 40.

No one knows exactly what causes asthma, and a cure remains elusive. But in recent years, great strides have been made in developing new treatments so that people with asthma can successfully manage the disease themselves, reducing symptoms and maintaining an active, satisfying life.

This section includes information on:

  • Need-to-know anatomy
  • Causes
  • Risk factors
  • Gastroesophageal reflux disease (GERD)
  • How asthma is classified
  • Need-to-know anatomy

    Asthma is a disease of the bronchial tubes, the airways of the lungs. When air is taken into the body through the nose and windpipe, it passes through the bronchial tubes and smaller bronchioles into tiny air sacs, called alveoli, that deliver oxygen to the blood. The air sacs also collect carbon dioxide from the blood, which is then exhaled.

    During normal breathing, the bands of muscle that surround the airways are relaxed, and air moves freely. During an asthma episode, or "attack," three main changes stop air from moving easily through the airways:

    • The bands of muscle that surround the airways tighten, narrowing the airways. This tightening is called a bronchospasm.
    • The lining of the airways becomes swollen or inflamed.
    • The cells that line the airways produce more mucous, which is thicker than normal.
    • Bronchospasms, inflammation, and mucus production cause asthma symptoms, which include wheezing, coughing, breathlessness, chest pressure, pain, or tightness. Severe episodes can lead to inability to perform normal activities like walking and talking.


      The airways in a person with asthma are very sensitive and react to many "triggers," although doctors don't know exactly why the triggers bring on asthma symptoms. People react differently to the various triggers, and an individual's reaction can vary from episode to episode. One of the most important steps in asthma control is avoiding triggers.

      Common asthma triggers include the following:

      • Infections (colds, viruses, flu, sinus infections)
      • Exercise (very common in children)
      • Weather (cold air, changes in temperature, and humidity)
      • Tobacco smoke and air pollution
      • Allergens (dust mites, pollens, pets, mold spores, cockroaches, and, rarely, foods)
      • Fumes from chemical products
      • Stress and strong emotions
      • Exposure to substances in the workplace (leading to occupational asthma)
      • Risk factors

        The number of people with asthma is on the rise, with more than 17 million Americans affected. More than 5 million of those are children. Although the exact causes of asthma are unknown, scientists have identified risk factors that make it more likely that a person will have asthma. They include the following:

        • Having a parent with asthma
        • Exposure to air pollution, as is common in large urban areas
        • Exposure to secondhand tobacco smoke
        • Exposure to chemicals or other substances on the job that can lead to occupational asthma
        • Low birth weight
        • Obesity
        • Sinusitis
        • Acid reflux, or gastroesophageal reflux disease (GERD)
        • Living in the inner city, which may actually be a combination of other risk factors, including exposure to air pollution and low birth weight
        • Occupational asthma

          Occupational asthma is caused or aggravated by exposure to substances in the workplace. For example, healthcare workers can develop an allergic reaction to latex gloves by breathing in the powdered proteins from the inner lining of the gloves. Workers in the chemical industry who are exposed to substances like ammonia can develop asthma due to irritation.

          Exposure to many substances used in industries can cause occupational asthma:

          • Chemicals such as adhesives, shellac and lacquer, plastics, epoxy resins, carpeting, foam and rubber, insulation, dyes, and enzymes in detergents
          • Proteins in animal hair and dander
          • Grains, green coffee beans, and papain, an enzyme derived from the papaya
          • Cotton, flax, and hemp dust, commonly found in the textile industry
          • Metals, such as platinum, chromium, nickel sulfate, and soldering fumes
          • If asthma is caused by occupational exposure, the symptoms usually are worse on workdays and improve when you are at home for any length of time. Symptoms include coughing, wheezing, chest tightness, and shortness of breath. Eye irritation, nasal congestion and a runny nose may also be present.

            If you think you have occupational asthma, ask your doctor about a referral to a specialist, most likely an allergist.

            Asthma and sinusitis

            Sinusitis is inflammation of the nasal passages around the nose and eyes. These passages are called sinuses. The sinuses warm, filter, and moisten air as we breathe. Symptoms of sinusitis include thick, colored drainage from the nose, coughing, post-nasal drip that may taste bad, headache, and head congestion, as well as a feeling of facial fullness or swelling, tooth pain, and sometimes fever.

            Sinusitis and asthma frequently coexist. When present, sinusitis can make asthma harder to treat. Remember that asthma is inflammation of the lungs and sinusitis is inflammation of the nasal passages. Controlling the inflammatory process in the nose can help lead to better control of asthma symptoms.

            Treatment of sinusitis includes use of anti-inflammatory nasal sprays (steroid nasal sprays) as well as antihistamine and decongestant medications. If the sinuses become infected, appropriate antibiotic therapy will be prescribed to treat the infection.

            Gastroesophageal reflux disease (GERD)

            It is estimated that more than 75 percent of patients with asthma also experience gastroesophageal reflux disease (GERD), the backward flow of stomach acids into the esophagus. People with asthma are twice as likely to have GERD as people without the condition-and those who have a severe, chronic form that is resistant to treatment are most likely to also have GERD.

            When acid enters the lower part of the esophagus, it can produce a burning sensation, or heartburn. If left untreated, GERD can eventually lead to lung damage, esophageal ulcers, and in some instances Barrett's esophagus, a condition that can eventually result in esophageal cancer.

            Doctors most often look at GERD as the cause of asthma when the following happen:

            • Asthma begins in adulthood.
            • Asthma symptoms get worse after a meal, after exercise, at night, or after lying down.
            • Asthma doesn't respond to the standard treatments.
            • Why do GERD and asthma coincide? One possible explanation is that the acid flow causes injury to the lining of the throat, airways, and lungs, making inhalation difficult and causing a persistent cough. Another possibility is that when acid enters the esophagus, a nerve reflex is triggered that causes the airways to narrow in order to prevent more acid from entering. This will cause shortness of breath. One study showed an increase in the rate of GERD in asthma patients treated with medications known as beta-adrenergic bronchodilators. However, further studies must be done before the relationship between GERD and these drugs can be understood.

              If you have both asthma and GERD, it is important that you consistently take any asthma medications your doctor has prescribed and that you control your exposure to asthma triggers as much as possible.

              Managing GERD

              To control symptoms of GERD, you should:

              • Avoid food and drink within three hours of going to sleep and take any medications your doctor has prescribed for acid reflux.
              • Raise the head of your bed by 6 inches to allow gravity to help keep the stomach's contents in the stomach. Do not use piles of pillows, because this puts your body into a bent position that can aggravate the condition by increasing pressure on the abdomen.
              • Eat smaller meals with moderate portions of food.
              • Maintain a healthy weight to eliminate abdominal pressure caused by extra pounds.
              • Limit consumption of fatty foods, chocolate, peppermint, coffee, tea, colas, and alcohol, all of which relax the lower esophageal sphincter. Also eat tomatoes and citrus fruits or juices sparingly, since their acid content can irritate the esophagus.
              • Give up smoking, which relaxes the muscle between the esophagus and stomach.
              • Wear loose belts and clothing.
              • Over-the-counter antacids can often relieve GERD symptoms. However, if after two weeks these medications have not helped, contact your doctor. You may need to be prescribed medications that limit the amount of stomach acid your body produces.
              • How asthma is classified

                Asthma is divided into four types, based on the frequency of symptoms as well as lung-function studies. Your physician will determine the severity of your asthma based on this information. A person's asthma can jump from one classification to another from day to day.

                Mild, intermittent asthma

                • Symptoms occur less than two times a week and nighttime symptoms occur less than two times per month.
                • Asthma episodes are brief, ranging from a few hours to a few days.
                • Performance on lung-function tests is greater than 80 percent of usual.
                • Mild, persistent asthma

                  • Symptoms occur more than two times per week but not every day.
                  • Nighttime symptoms may occur more than two times per month.
                  • Episodes may affect activity.
                  • Performance on lung-function tests is greater than 80 percent of usual.
                  • Moderate, persistent asthma

                    • Symptoms occur daily.
                    • Asthma episodes affect normal activity, occur more than two times per week, and may last for days.
                    • There is a reduction in lung function to between 60 percent and 80 percent of usual.
                    • Patient uses quick-relief medication daily.
                    • Patient experiences nighttime symptoms more than once a week.
                    • Severe, persistent asthma

                      • Symptoms occur continuously with frequent nighttime symptoms.
                      • Normal daily activity is limited.
                      • Lung function is less than 60 percent of usual.
                      • Though asthma cannot be cured, it can be controlled. Frequent symptoms, trouble sleeping, difficulty completing tasks, and trips to the emergency room can be avoided with preventive steps and appropriate treatment.

                        Last reviewed on 8/26/08

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