rhinitis%20-%20allergic
RHINITIS - ALLERGIC
Allergic rhinitis is a symptomatic disorder of the nose secondary to IgE-mediated inflammation of the nasal membranes induced after exposure to allergens.
Major symptoms include nasal itching, watery rhinorrhea, nasal obstruction/congestion, sneezing and postnasal drainage.
Other symptoms include headache, conjunctival symptoms, eye pruritus, impaired smell and morning cough.
Symptoms can reverse spontaneously with or without treatment.

Definition

Rhinitis

  • Inflammation of the nasal lining membranes

 Allergic Rhinitis

  • A symptomatic disorder of the nose secondary to IgE-mediated inflammation of the nasal membranes induced after exposure to allergens

Signs and Symptoms

Major Symptoms

  • Nasal itching
  • Watery rhinorrhea
  • Nasal obstruction/congestion
  • Sneezing
  • Postnasal drainage

Other Symptoms

  • Headache
  • Conjunctival symptoms, eye pruritus
  • Impaired smell
  • Morning cough
  • Sleep problems/excessive daytime sleepiness/sleep-disordered breathing or obstructive sleep apnea

Symptoms can reverse spontaneously with or without treatment

Pathophysiology

  • There may be various diatheses for allergic rhinitis sensitization but the most important mechanisms are:
    • Genetic factors 
    • Production of IgE antibody 
  • Most allergic rhinitis are caused by inhalation antigens such as:
    • Dermatophagoides (antigen in house dust) - most common
    • Pollens (eg trees, grasses and weeds) - most common
    • Fungi
    • Pets
  • Two phase reactions:
    • Early phase reaction happens when histamine and leukotrienes are released from mast cells and irritate the sensory nerve endings and blood vessels of the nasal mucosa
      • This irritation causes sneezing, rhinorrhea (watery), nasal mucosal swelling or blockage 
    • Late phase reaction happens when inflammatory cells like activated eosinophils infiltrate the nasal mucosa that is exposed to these antigens
      • Seen 6-10 hours after the exposure to antigens
      • Causes mucosal swelling
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