Allergic Rhinitis

ALLERGIC RHINITIS
PATHOGENESIS OF ALLERGIC RHINITIS
  • Allergic rhinitis is a type I hypersensitivity. It occurs in two phases:
  •  Initial response/Acute or early phase
  • Antigen specific Ig E antibodies bind to the surface receptors of mast cells and basophils.
  • The process from first antigen exposure to the coating of mast cells by Ig E acts as sensitization (prior sensitization), called priming or sensitizing exposure (dose).
  • Subsequent exposure (shocking dose) to same antigen then results in activation of mast cells and basophils with release of inflammatory mediators 
  • Histamine (most important)
  1. PAF
  2. Heparin
  3. Cytokines (IL-1, 3, 4, 5, 6; INF)
  4. Leukotriens (B4, Ch D4)
  5. Eosinophil chemolactic factor (ECF)
  6. PGD2
  7. Neutrophil chemolactic factor (NCF)
  • The release of these mediators result in : -
  1. Increased vascular permeability and vasodilatation which result in tissue edema - Nasal blockage and sneezing.
  2. Smooth muscle spasm → Bronchoconstriction
  3. Hyperactivity of glands → Rhinorrhea
  4. Recruitment of inflammatory cells.
2. Late phase response
  • Recruited inflammatory cells of initial phase amplify and sustain the inflammatory response without additional exposure to the triggered antigen.
  • PAF is the most important mediator in initiation of late phase response. 
  • Eosinophils are particularly important cells among the recruited cells which also include neutrophils, basophils, monocytes and T-cells. 
  • It causes symptoms like nasal congestion and post nasal drip.
CLINICAL TYPES OF ALLERGIC RHINITIS
  1. Seasonal:Hay fever due to pollen grains that occur at the time of pollination season.
  2. Perennial:It affects the patient throughout the year.
CLINICAL FEATURES OF ALLERGIC RHINITIS Symptoms:
  • Itching in the eyes and nose.
  • Watery discharge from the eyes and nose.
  • Allergic Rhinits is a most common cause of Nasal Discharge.
  • Paroxysmal Sneezing
  • Nasal Obstruction-may lead to Rhinolalia Clausa.
  • Anosmia,Headache.
  • It does not lead to Epistaxis.
Signs:
  • Nasal Mucosa appears pale and swollen.
  • Allergic Salute:Itching in the nose and rhinorrhea may lead the patient to lift the tip of his nose upwards with his palm which appears like a salute.
  • Darrier's Line:Repeated allergic salute may result in a horizontal line on the nasal dorsum a little superior to the tip of the nsoe.
INVESTIGATIONS IN A CASE OF ALLERGIC RHINITIS
  • Immediate hypersensitive skin test : Most valuable tool for identifying the causative antigen in Allergic Rhi­nitis.
  • The radioallergosorbent test (RAST):Though accurate, is more expensive and less dis­criminative than skin testing.
  • Elevated immu­noglobulin E (IgE) levels :Observed in only 30%-40% of patients with allergic rhinitis and may be secondary to other unrelated dis­orders.
  • Although eosinophils are usually iden­tified in nasal secretions from patients with al­lergic rhinitis, they are also detected in eosinophilic nonallergic rhinitis and hyperplas­tic sinusitis.
  • Eosinophil count:peripheral eosinophilia seen in a peripheral blood smear is an inconsistent finding.
TREATMENT IN A CASE OF ALLERGIC RHINITIS
  • Avoidance of Allergens.
  • Medications:Antihistaminic,Steroids(generally Nasal Steroids is used.Systemic steroids in case of Severe Allergic Rhinitis),Leukotriene Antagonist like Montelukast. Immunotherapy:Specific desensitization against known Allergens.
  • Surgery: done in a case of allergic rhinitis when other methods have failed or when there is marked septal deviation or bony turbinate enlargement which makes topical nasal spray usage difficult.
  • Radiofrequency ablation/Laser ablation of the inferior turbinate or Inferior turbinectomy.
  • It should never be used as first line of treatment.
DIFFERENTIAL DIAGNOSIS OF ALLERGIC RHINITIS
  •  Vasomotor Rhinitis:Imbalance of Autonomic Nervous System is considered to be the cause.
  • Sneezing is less.but blocking and rhinorrhoea dominate.
  • Vidian Neurectomy may help. Churg-Strauss syndrome
  • :Allergic rhinitis is associated with peripheral eosinophilia, cutaneous purpura, mononeuritis, asthma and small-vessel vasculitis .
Exam Question
  • Immediate hypersensitivity skin test is most useful in diagnosis of allergic rhinitis.
  • When small-vessel vasculitis is associated with peripheral eosinophilia, cutaneous purpura, mononeuritis, asthma, and allergic rhinitis, a diagnosis of Churg-Strauss syndrome is considered.
  • Rhinolalia Clausa may be associated with Allergic Rhinitis.
  • Early mediators of allergic rhinitis are Leukotriene ,IL-4 ,IL-5.
  • In Allergic rhinitis nasal mucosa is Pale and swollen.
  • Surgical procedure like Radiofrequency ablation/Laser ablation of the inferior turbinate or Inferior turbinectomy may be done in a case of Allergic Rhinitis.
  • Treatmentof Allergic Rhini s includes avoiding allergen,corticosteroids,surgery.
  • Allergic Rhinitis does not leads to Epistaxis.
  • Most common cause of Nasal Discharge is Allergic Rhinitis.
  • Histamine is a preformed toxin involved in mechanism of allergic rhinitis.
  • Allergic rhinitis is a type 1 hypersensitivity reaction.
  • Allergic salute is seen in Allergic Rhinitis.
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