response generally occurs. This reaction is attributed largely
to the interaction between the allergen, IgE, and the sensitized
mast cell, resulting in mast cell degranulation. Other cells, including
basophils, play an important role as well. As a result,
mediators of the allergic response, including histamine, are released
along with various chemotactic factors, which amplify
and perpetuate the allergic response. Because these mediators
are already present in the mast cell, they act within minutes
to cause the common symptoms of allergic rhinitis, including
itching, sneezing, and congestion.28,29,30
Histamine receptors (H1) are present throughout the nasal
mucosa and their activation results in vascular engorgement,
leading to nasal congestion, direct stimulation of mucus
secretion, and increased glandular secretion.30 In addition,
parasympathetic nervous system stimulation results in cholinergically
mediated nasal secretions. Finally, stimulation of
peripheral nerve receptors results in itching and sneezing
reflexes.19