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Allergic rhinitis causes, pathogenesis, symptoms, investigations, treatment

Definition: Rhinitis is defined clinically by a combination of two or more nasal symptoms: running nose, blocking, itching, and sneezing. Allergic rhinitis occurs when these symptoms are the result of IgE-mediated inflammation, following exposure to allergen.

Etiology (Causes, predisposing and exciting factors)

(A) Predisposing factors:

  • Genetic predisposition: it is the best established risk factor, gene involved in atopy include loci on 5q, 11q, and 12q.
  • Living in developed countries, pollution, climate interaction, and good hygiene, all seem to be risk factors.
Allergic-rhinitis-approach


(B) Exciting factors: 

The globally important allergens are: house dust, mites, grass, tree and weed pollen, pets, cockroaches and moulds.
Exciting-factors-allergic-rhinitis


Incidence: 
Quoted provenance figures vary widely from 1 to 40%.
May be: seasonal, perennial, or mixed.

Classification:
Classification-allergic-rhinitis

Pathogenesis: type I hypersensitivity

Pathogenesis-allergic-rhinitis
  1. Sensitization: allergen is captured by Langerhans cells……stimulate IgE production by B cells.
  2. Subsequent reaction to allergen (early phase), with release of mediators like histamine, leukotrienes, prostaglandins, and C4, causing sneezing, itching, rhinorrhea, and nasal block.
  3. Late phase reaction: in half of patients, involves the ingress of eosinophils, basophils, mast cells, T lymphocytes, neutrophils, and macrophages to tissues.

Pathology:

  • Edema.
  • Infiltration with eosinophils & plasma cells.
  • Watery discharge with high serous content.
  • Vascular dilatation, stasis leads to purple color.
  • Polypi: pedunculated edematous mucosa.
  • Superadded infection: red mucosa and viscid discharge.

Symptoms:

  • Nasal itching & sneezing.
  • Bilateral watery discharge may be postnasal drip.
  • Bilateral or alternating nasal obstruction.
  • Anosmia, continuous or intermittent.
  • Asthma: most asthmatics have rhinitis, and about one third of rhinitis patients have asthma.

Signs:

  •  Edematous pale blue mucosa.
  •  Excessive watery secretions.
  • Swollen edematous turbinates.
  •  May be allergic nasal polypi.
  • In children: allergic salute.
signs-allergic-rhinitis-bullae

Investigations: Following history and examination

  • Nasal cytology: eosinophilia.
  • Skin prick testing
      Technique: forearm skin is pricked with needle passed via diluted different allergens
      Results: Positive…... Central wheel surrounded by erythema.
      Value : Confirm suspected allergen …. In relation to history.
  •  Nasal challenge test.
     Technique: Diluted aqueous extract sprayed in the nose
  • Blood examination.
      -Eosinophilia. -Increased total IgE.
      -Increased plasma IgE level to specific Ag.

Treatment of Allergic rhinitis: 

(A) Medical:


  1. Avoid exposure to offending antigen.
  2. Hypo sensitization (Immunotherapy) to form IgG (blocking antibodies).
  3. Mast cell stabilizers: sodium chromoglycate (spray 4-6 times daily).
  4. Antihistaminics: astemizole, loratadine, fexofenadine (oral or nasal spray).
  5. Steroids: topical, systemic, or depot. Topical steroids are considered the most effective treatment for rhinitis.
  6. Ipratropium bromide: useful against watery rhinorrhea.
  7. Nasal drops for short time to avoid rhinitis medicamentosa.
  8. Oral decongestants.
  9. Recently antineutrinos: effective against congestion and edema, useful in nasal polyposis.


(B) Surgical:


  1. Turbinate reduction.
  2. ESS, for sinonasal polyposis.
  3. Vidian neurectomy (rarely done now).

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