It's an immune response to any foreign body:

1)Bronchoconstriction (Type 1 hypersensitivity)

2)Bronchial inflammation (inflammation and increased mucus poduction, pluggin the airways)

3) foreign bodies finding their way in to the inner airways are ingested by APC's which then present the allergens to other cells of the immune system which then triggers a further immune response, the humoral immuune system etc.

More inflammatory mediators are released causing remodelling of the airways for the duration of the asthma attack.

Basicaly:

Foreign body--> Stimulus--> Immune response --> Inflammation--> Airway constriction/increased mucus production/increased release of inflammatory mediators in airways (Mast cells = histamine, leukotrienes, ) (Tachypnea/dyspnea/orthopnea)

Airway cell lining becomes leaky and oedematus.