Allergic Rhinitis: Causes, Symptoms, Risk factors, Diagnosis, Management
Allergic rhinitis is a collection of symptoms that occur if you are exposed to substances you are sensitive to. This reaction by your body is known as an ‘allergy’. Allergies can be seasonal, occurring especially in the spring and fall if you are allergic to pollen from trees and grass, for instance. Allergies can also be year-around if, for example, you are allergic to pets or house dust mites. House dust mites occur everywhere in a house and are too small to be seen.Seasonal allergies are also known as ‘hay fever’.
1. Type I hypersensitivity reaction.
- The initial response is an allergen, such as pollen, being presented to the nasal mucosa. This allergen is recognized as an antigen by an antigen-presenting cell and presented to plasma cells. These cells subsequently produce IgE and attach themselves to mast cells awaiting re-exposure.
- Upon re-exposure, an antigen antibody complex is formed and the mast cell degranulates. During degranulation, histamines, leukotrienes, platelet activating factor as well as other factors are released.
- Nasal mediators such as histamine are responsible for the early phase reaction, which includes patient symptoms such as sneezing, rhinorrhea and congestion.
- Additional nasal mediators are released including the cytokines, IL4 and IL5 which result in recruitment of additional cells to the nasal mucosa. These cells include Eosinophils, additional mast cells and basophil cells. It is this environment which sets up the hyper-responsiveness of the nasal mucosa as well as priming of the nasal mucosa. A predominant symptom in this phase is nasal congestion. It occurs 2 to 5 minutes of antigen antibody reaction.
2. A second (late) phase is the result of mediator release from cells (neutrophils, eosinophils) and occurs about 4 to 6 hours after the acute phase.
- nasal congestion
- postnasal drainage (throat-clearing and cough).
- Seasonal or perennial, & linkage with known exposure to allergens.
Signs: the classic signs of the
- allergic salute (upward rubbing of the nose with the palm of the hand),
- allergic shiners (darkening of the lower eyelid due to chronic nasal obstruction), and allergic crease (a line in the skin above the tip and below the bridge of the nose caused by constant rubbing).
- With chronic nasal obstruction, many AR children will make use of the oral airway and manifest a gaping mouth appearance. open-mouthed “adenoid facies.”
- itchy, red, and watery eyes. puffiness around the eyes.
- Pale nasal mucosa & clear rhinorrhea (in the absence of secondary infection). Polyps may be present.
- high arched palate, prominent pharyngeal lymphoid
- Blockage of the Eustachian tubes,
- cough, and a sensation of pressure in the sinuses result from edema and venous engorgement of the nasal mucosa.
Risk factors :
- family history of atopy, high serum IgE levels before six years of age, and exposure to indoor allergens such as animals or dust mites.
- The natural history of allergic rhinitis includes an onset that is common in childhood, adolescence or early adulthood. Symptoms often wane in older adults but may develop or persist at any age.
- There is no apparent gender selectivity or predisposition and allergic rhinitis may contribute to other conditions including sleep disorders, fatigue or learning problems.
- The allergic response is a complex allergy driven mucosal inflammation including a number of inflammatory cells, mediators and cytokines. There is an early phase response, a late phase response and a priming response.
Diagnosis: can generally be made on the basis of the history and physical examination.
- Nasal smears (Hansel’s stain) à eosinophils (> 25% of the cells).
- total IgE
- skin test: introducing the suspected allergen under the skin and allowing it to react with IgE bound to mast cells à wheal-and-flare response e.g. abrading or scratching, prick test, Intradermal tests, skin endpoint titration (SET).
Investigation: detect signs of rhinitis and conjunctivitis and may reveal wheezing suggestive of associated asthma.
- Spirometry is useful in detecting sub clinical asthma, and computed tomography most reliably reveals sinusitis in patients with symptoms of refractory rhinitis.
- Additional testing may be helpful if the diagnosis is uncertain or if the response to therapy is suboptimal. For example, blood or nasal eosinophilia suggests an allergic cause, whereas neutrophilia points to an infectious cause.
When managing patients with allergic rhinitis, four general principles of management should be considered.
Level I: Prevention and Control of Symptoms.
- Environmental Control
- First-line Pharmacotherapy:
Antihistamines compete with histamine for H1-receptor sites on the target organs during the allergic response
Decongestants are sympathomimetic substances that cause vasoconstriction within turbinate stroma, producing shrinkage of congested tissue (Pseudoephedrine & Phenylpropanolamine)
Comolyn nasal spray: stabilizes and protects mast cells from degranulation
Level II: Recognition and Management of Complicating Factors
- Treat other types of rhinitis: vasomotor, medicamentosa
Level III: Corticosteroids for Control of Severe or Chronic Symptoms
- ameliorate the effects of both acute and late-phase allergic reactions
- intraturbinal injection
Level IV: Immunotherapy
- symptoms are not controlled with pharmacotherapy, allergens that cannot be avoided, symptoms span two or more allergy seasons, willing to cooperate in a program of immunotherapy
- parenteral administration of antigens à formation of allergen-specific IgG-blocking antibodies à compete with IgE antibodies for target sites on mast cells or basophils.