An allergy is an overreaction by the immune system to a typically harmless substance, known as an allergen. When a sensitive person inhales airborne particles (pollen, mold spores, or dust mite debris), the immune system mistakenly identifies them as threats. The respiratory system, from the nose down into the lungs, is a primary site for this immune response. This interaction triggers an inflammatory cascade that significantly impacts breathing and lung function.
How Allergies Trigger Lung Inflammation
The initial step involves specialized immune proteins called Immunoglobulin E (IgE) antibodies. These IgE antibodies are produced in response to the allergen and attach to mast cells, immune cells located throughout the respiratory lining. When the person is exposed again, the allergen particles bind to and “cross-link” the IgE antibodies on the mast cell surface.
This cross-linking signals the mast cell to rapidly release chemical mediators in a process called degranulation. Histamine is the most well-known mediator, responsible for immediate allergy symptoms like itching and swelling. Mast cells also release newly formed mediators, including cysteinyl leukotrienes, which powerfully constrict the airways.
These released chemicals act directly on lung tissues, causing two main physical effects. Histamine and leukotrienes cause the smooth muscles surrounding the airways to contract, a process called bronchoconstriction, which narrows air passages. They also increase mucus production and cause swelling in the lining of the bronchi, which further restricts airflow.
Common Allergic Respiratory Conditions
When allergic inflammation affects the lower airways, it often leads to allergic asthma. This chronic condition is characterized by recurring episodes of wheezing, shortness of breath, chest tightness, and a persistent cough. Allergic asthma is the most common form of asthma, with many individuals testing positive for sensitivity to airborne allergens like pet dander, pollen, or dust mites.
This chronic state means the airways remain hypersensitive and inflamed, making them prone to reacting strongly to the allergen and to non-allergic triggers like cold air or exercise. The inflammation is frequently associated with an increase in eosinophils, a type of white blood cell, in the airway lining. These cells contribute to ongoing inflammation and can lead to structural changes in the airway tissue over time.
While allergic asthma is the most frequent lung condition, Allergic Bronchopulmonary Aspergillosis (ABPA) is a less common, severe issue. ABPA occurs in people with asthma or cystic fibrosis who develop an allergic reaction to the common environmental mold Aspergillus fumigatus. ABPA causes chronic inflammation, leading to mucus plugging in the airways and potentially permanent lung damage.
Identifying and Managing Allergic Lung Issues
Identifying allergic triggers is a first step in managing allergic lung issues. Clinicians often use allergy skin prick tests, which involve placing small amounts of various allergens on the skin to check for a localized reaction. Blood tests that measure the level of specific IgE antibodies in the circulation can also help pinpoint the responsible allergens.
To assess the impact of allergies on lung function, spirometry is performed. This test measures how much air a person can exhale and how quickly they can do it, providing objective data on airway obstruction. In some cases, a bronchoprovocation test may be used to see how sensitive the airways are to a trigger like methacholine.
Management of these conditions centers on two primary strategies: avoidance and medication. Reducing exposure to identified triggers—such as using allergen-proof covers on bedding for dust mite allergies or using high-efficiency particulate air (HEPA) filters—can significantly lessen symptoms.
Pharmacological treatment involves two main categories of medication. Quick-relief inhalers, known as bronchodilators, rapidly relax the tight muscles around the airways to treat acute symptoms. Long-term controller medications, most often inhaled corticosteroids, are taken daily to reduce the underlying inflammation and airway swelling. For patients whose symptoms are difficult to control, allergy immunotherapy can be administered over several years. This treatment fundamentally changes the immune system’s response to the allergen, leading to reduced sensitivity and fewer symptoms.