A localised allergic reaction; typically from pollen, animal fur or dust, made worse by pollutants and exercise, anxiety/stress.
Allergens cause white blood cells in bronchi and bronchioles to release histamine causing airways to become inflames and more mucus to be produced by epithelial cells. Fluid leaves capillaries and enters the airways, hence greater resistance to air flow in and out.
Symptoms:
Difficulty breathing - bronchi and bronchioles are constricted and filled with mucus
- diameter of airways is reduced
- mucus creates a longer diffusion pathway so less oxygen can diffuse in
Wheezing sound when breathing - caused by air passing through the constricted bronchi and bronchioles
Tight feeling in chest - as not able to ventilate lungs properly
Coughing - reflex response to try to clear obstructed bronchi and bronchioles of mucus
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