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.