Also called: Bronchial Asthma, Allergic Rhinobronchitis, Allergic Bronchitis, Combined Allergic Rhinitis & Asthma Syndrome
Allergic asthma is an allergic inflammation in the lower airway of the respiratory system. It involves the simultaneous presence of both asthma and respiratory allergies, particularly hay fever (allergic rhinitis). According to the U.S. National Institute of Environmental Health Sciences, 10 million people in the United States suffer from allergic asthma.
An allergy occurs when the immune system identifies a harmless substance as being dangerous and releases antibodies to fight the substance. Any substance may cause an allergic reaction and any substance that causes this reaction is called an allergen.
Allergic asthma – also known as allergic bronchitis – is different from non-allergic bronchitis, which is often linked to a severe cold or flu. Non-allergic bronchial conditions are caused by a bacterial, viral or fungal infection. Conditions normally resolve after treatment with medication, or on their own after several days.
Allergic asthma is a serious condition that requires examination by a physician. The physician will perform tests to identify what specific substance is triggering the allergy, and then develop methods to avoid the allergen. Medications may be necessary to reduce inflammation, open the airways and provide relief of symptoms.
About allergic asthma
Allergic asthma is an allergic reaction to a particular substance, resulting in asthma symptoms affecting the lower respiratory system (including the lungs). Other terms have been used to describe this condition including extrinsic asthma, allergic bronchitis, bronchial asthma, allergic rhinobronchitis, combined allergic rhinitis and asthma syndrome.
In order to understand allergic asthma and its connection with allergies, some basic information on the nature of the respiratory system is necessary.
The respiratory system brings oxygen into the lungs and transfers the oxygen to the blood, where it exchanges the oxygen for carbon dioxide that is exhaled from the nose and mouth. Air enters through the nose and mouth, passes into the throat and windpipe, and branches into two smaller airways (bronchi) that divide into smaller tubes (bronchioli) that then supply air to the two lungs. The airways look like an upside-down tree, which is why it is called the bronchial tree.
An essential part of the respiratory system, the bronchi can become inflamed due to infection, irritation or allergies. An allergy is an exaggerated or inappropriate immune system reaction to a harmless substance. People may have allergies to any type of substance, but allergic asthma is most often triggered by airborne allergens such as pollen, mold, dust or animal dander.
Allergic asthma is the most common form of asthma, a chronic inflammatory disorder of the lungs in which the airways become blocked or narrowed and cause difficulty breathing and shortness of breath. Although the symptoms of allergic asthma and non-allergic asthma are the same, the conditions are caused by different factors. Non-allergic asthma is triggered by environmental factors that include exercise, cold or warm temperatures and sudden changes in temperature. Allergic asthma, however, is triggered only by allergens, which are often inhaled deep into the airways where they cause bronchial constriction. By avoiding allergic reactions, people with allergic asthma can prevent asthma attacks.
Recent research has demonstrated a link between the upper respiratory system (nose, sinuses and throat) and the lower respiratory system (lungs and bronchi). The entire respiratory system is composed of the same type of cell tissue and this tissue reacts similarly to inhaled allergens or other irritants. This connection between the upper and lower airways is believed to be associated with allergic asthma, which often involves upper and lower respiratory symptoms.
Because allergic asthma is more common in people who have a family history of allergies or asthma, the disease is often considered a hereditary condition. However, other respiratory conditions can also impact the airways and increase a person’s risk of developing allergic asthma.
Though the two are similar, allergic asthma has a different origin than cold and flu-related bronchitis (non-allergic bronchitis). Allergic asthma may be misidentified as acute bronchitis (a type of non-allergic bronchitis) and the methods of treatment and prevention for that condition will not work on allergic asthma.
Potential causes and risk factors
Allergies are considered a risk factor for allergic asthma. According to the American Academy of Allergy, Asthma & Immunology (AAAAI), most people with asthma also suffer from other allergic disorders. Allergies may be caused by any substance and result in a variety of different symptoms. Allergies are caused by the body producing an antibody (IgE) that is directed at the allergen. The antibody triggers the body to release histamines that produce the allergic reaction. Allergens that commonly trigger allergic asthma include:
- Cockroach debris
- Animal dander
- Dust and dust mites
People with allergic rhinitis (hay fever) are particularly at risk for developing allergic asthma. This is because hay fever symptoms, such as a stuffy nose, often cause people to breathe through their mouths. The nasal passages are lined with tiny hair-like structures called cilia that act like filters, preventing harmful particles from entering the body. When people breathe through their mouths, these filters are bypassed and particles can proceed directly to the lower respiratory system (e.g., lungs). New research is examining the occurrence of the three diseases and the overlap between patients with one or more of these diseases. There are high risk factors for patients with allergic rhinitis to develop asthma due to the physical relationship between the upper and lower airways of the respiratory tract. Allergic rhinitis may cause patients to breathe through the mouth instead of the nose which prevents the natural filtering of air through the nose, and contributes to the inhalation of allergens into the lower airways.
Related conditions for allergic asthma
Allergic asthma may be confused with non-allergic forms of bronchitis. There are two different types of non-allergic bronchitis:
- Acute bronchitis. An infection of the bronchial tree due to a virus, bacteria or fungi. Many of the same viruses that cause common colds also cause bronchitis. Acute bronchitis is often a viral condition, which means it will not respond to antibiotics, and is contagious. Symptoms usually resolve after several days to a week, though coughing may persist for longer periods.
- Chronic bronchitis. A condition characterized by the overproduction of mucus by the cells lining the larger breathing tubes (bronchi). The mucus blocks the movement of air and contributes to the development of infections. Chronic bronchitis is defined by the presence of a mucus-producing cough most days of the month for at least three months of the year for two successive years without any other underlying disease to explain the cough. Smoking is the most common cause of chronic bronchitis. Chronic bronchitis symptoms also intensify when the individual is exposed to air pollutants.
The treatment of chronic bronchitis is aimed at reducing the irritation in the bronchial tubes. Some patients with chronic bronchitis also have an acute bacterial infection that may be treated with antibiotics. Patients that are prescribed antibiotics will only take them until the bacterial infection is resolved, after which chronic bronchitis symptoms may still be present. Patients with chronic bronchitis should not take antihistamines as the medication dries the mucus in the chest and may cause breathing problems.
Chronic bronchitis is often neglected until it is in an advanced state. Frequently the lungs have been seriously injured by the time the patient consults a physician.
Another condition that can mimic allergic asthma is chronic rhinosinusitis (also known as sinusitis), a chronic infection of the sinus cavities. The signs and symptoms of chronic rhinosinusitis include a yellow-green mucus discharge and chronic cough.
Signs and symptoms of allergic asthma
The signs and symptoms of allergic asthma are similar to those of non-allergic asthma and may include:
- Shortness of breath
- Chest tightness
- Runny nose
Allergic asthma may also be identified by colds that continually affect the chest or last for longer than ten days.
Diagnosis methods for allergic asthma
Diagnosis of allergic asthma begins with a trip to the physician. The physician will review the patient’s medical history, ask questions and conduct a physical examination including listening to the chest with a stethoscope. The physician may also recommend a chest x-ray to check for lung disease or pneumonia, a sinus x-ray and a sputum culture, which is a test that checks for the presence of bacteria in coughed-up mucus.
Additional tests may be performed to identify other potential causes for allergic asthma symptoms. A pulmonary function test (PFT) may be necessary. The PFT is a painless and noninvasive test that measures lung function. A PFT involves the patient exhaling into a spirometer, a device that measures the volume of air in the lungs and determines how quickly the patient can get air out of the lungs. The PFT results will indicate to the physician the patient’s lung function.
Allergy skin tests may be performed to identify specific substances to which the patient is allergic. Skin testing is fast and simple and involves introducing a small amount of allergen to the skin to provoke a reaction. A positive test for an allergen occurs when the skin reddens and swells.
Blood tests may be performed to determine the amount of a particular substance in the blood and identify abnormally high or low levels. Blood tests will involve drawing blood from the patient and sending the blood to a laboratory for analysis. Blood tests may cause discomfort but are generally not painful.
Difficulty in diagnoses or in treatment may require the physician to perform thorough tests that examine the specific structure of the nose and upper and lower airways of the respiratory system. The following diagnostic tests may be performed in some cases of allergic asthma:
- Anterior rhinoscopy. This procedure allows the physician to examine the inside of the nose. This will help the physician determine whether the symptoms are caused by nasal abnormalities like polyps. The procedure will cause no discomfort.
- Nasal endoscopy. A special telescope is inserted into the nose and/or sinus cavities to allow the physician to examine those areas. It can be used for both diagnosis and as a guide during surgical procedures.
- Computed axial tomography (CAT) scan. This test will show cross-sectional images of the inside of the head. The test will allow the physician a three dimensional view of the sinus cavities and determine the healthiness of the sinuses. The patient may be required not to eat or drink before the test. The test will take 15 to 30 minutes to perform and does not cause discomfort.
Treatment and prevention of allergic asthma
Although allergic asthma is not curable, it is a treatable condition. The most important steps in treatment are the identification and avoidance of the allergens that trigger the condition. If the patient knows what substance to avoid, it is much easier to develop ways to avoid it. Even when allergen avoidance is accomplished, it may take months or years to reverse airway symptoms to the substance.
Allergens cannot always be avoided. Therefore, patients may need medication to help control their symptoms. Bronchodilator drugs may be prescribed to help relax the muscles and open up the air passages. These medications may come in inhalers, where the patient breathes the medication directly into the lungs. Anti-inflammatory medications like corticosteroids are also inhaled and help to reduce swelling of the airways. These medications may be used together to treat both short- and long-term symptoms.
Antihistamines are another type of medication that may be used in allergic asthma treatment. They block the effect of histamines, chemicals released during an allergic reaction. Antihistamines may be used continuously as a prevention method for allergic asthma. Continuous use helps to control allergy symptoms and inflammation. Methods for continuous use will be defined by the physician but normally involve taking antihistamines daily as prevention even if no symptoms are present. Some physicians do not favor the use of antihistamines for asthma because of the drugs’ tendency to dry out the individual and reduce secretions.
Allergy shots (immunotherapy) may be an option for some patients with allergic asthma to reduce the risk of allergic reaction. Allergy shots are given to patients to build up a resistance to the substance to which they are allergic. Allergy shots increase a person’s tolerance to an allergen, which helps prevent or reduce symptoms.
Ongoing research on allergic asthma
There are numerous research initiatives examining the relationships between allergies and asthma. Drug research is also ongoing and new drugs are being identified to assist patients in allergy and disease management. Ongoing research includes:
- “One airway” disease and the development of “total airway” specialists. Many people with non-allergic asthma, allergic rhinitis or allergic asthma see different specialists for treatment and prevention. Recent research has indicated that the relationship between the upper and lower airways is strong and similar to a continuum. The concept behind “total airway” specialists would reflect the relationship between the airways within the body and coordinate the professional knowledge, diagnostic methods and treatment of these related conditions.
- Drug research. Leukotriene modifiers are a relatively new class of drugs used in the treatment of asthma and some allergies. Leukotrienes are chemical compounds released in the body during inflammation, which cause the airways to narrow. Leukotriene modifiers block the production or action of leukotrienes. Leukotriene modifier research indicates that these drugs are effective in combination with inhaled corticosteroids for the treatment of mild to moderate asthma, particularly allergic asthma. Leukotriene modifiers may help to reduce patient reliance on high doses of inhaled corticosteroids. Leukotriene modifiers are taken once daily and the ease of administration makes the medication readily tolerated by patients.
- World Health Organization (WHO). WHO activities in asthma research include a number of international studies and initiatives. The United States is involved in all of these WHO studies and initiatives, including:
- The International Study of Asthma and Allergies in Childhood (ISAAC) is examining the relationship between air pollution and childhood asthma.
- The Global Initiative for Asthma (GINA) is examining ways to cut the death and disability rates due to asthma through developing the best strategies for asthma management and prevention.
- The Allergic Rhinitis and Impact on Asthma Initiative (ARIA) is aimed at developing a strategy to prevent bronchial asthma through the management of allergic rhinitis.
- The International Study of Asthma and Allergies in Childhood (ISAAC) is examining the relationship between air pollution and childhood asthma.
Questions for your doctor
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions regarding allergic asthma:
- Do my symptoms suggest allergic asthma?
- What methods will you use to determine if I have allergic asthma?
- Is the condition dangerous to my overall health?
- What may have caused me to develop this condition?
- What may be triggering my asthma symptoms?
- What methods will you use to determine the trigger of my allergic asthma?
- What treatments are available to me?
- Do I need to treat my symptoms when they occur – or will treatment be ongoing, even when I don’t have symptoms?
- Will I have to take medication for the rest of my life?
- What steps can I take to avoid the allergens which trigger my allergic asthma?
- Will the condition flare-up at certain times or will symptoms appear consistently year-round?
- Are my children more likely to develop allergic asthma because I have the condition?