What are the causes and prevention methods for allergic rhinitis?

Allergic Rhinitis: Causes and Prevention

Causes of Allergic Rhinitis

Allergic rhinitis is caused by IgE-mediated immune responses to environmental aeroallergens, which trigger inflammation of the nasal mucosa and produce characteristic symptoms of sneezing, nasal itching, rhinorrhea, and nasal congestion. 1

Primary Allergen Categories

Seasonal allergens (causing hay fever):

• Outdoor pollens from trees, grasses, and weeds that occur during specific seasons 2
• These allergens are difficult to avoid through standard environmental control measures 1

Perennial allergens (year-round exposure):

• Indoor dust mites - the most common perennial allergen 1
• Animal dander from pets, particularly cats and dogs 1
• Mold spores in indoor environments 2
• Cockroach allergens in some environments 1

Pathophysiology

The condition develops when genetically susceptible individuals produce specific IgE antibodies to these environmental allergens, leading to mast cell degranulation and release of inflammatory mediators including histamine and leukotrienes upon re-exposure 3. This IgE-mediated response must be confirmed through skin testing or blood tests for specific IgE to establish the allergic basis of symptoms 1.

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Prevention Strategies

Primary Prevention: Continuous Pharmacologic Therapy

For patients with established allergic rhinitis, continuous daily intranasal corticosteroid therapy is the most effective prevention strategy for symptom recurrence and should be used throughout allergen exposure periods rather than intermittently. 4

• Intranasal corticosteroids are the single most effective monotherapy and should be the cornerstone of prevention for patients whose symptoms affect quality of life 1
• These medications work by reducing inflammation and preventing symptom development when used proactively before allergen exposure 1
• For seasonal allergies, starting intranasal corticosteroids before the pollen season begins significantly reduces symptom severity 1

Environmental Control and Allergen Avoidance

While allergen avoidance alone is usually inadequate for outdoor allergens, specific environmental controls should be implemented for identified indoor allergens that correlate with clinical symptoms. 1

For pollen allergies:

• Keep windows and doors closed during high pollen seasons 4
• Avoid outdoor activities when pollen counts are elevated 4
• Use air conditioning rather than attic fans 4

For dust mite allergies:

• Consider removing carpeting from bedrooms 1, 4
• Use allergen-impermeable bed covers (mattress and pillow encasements) 1, 4
• Apply acaricides (chemical agents that kill dust mites) 1
• Use air filtration systems 1
• Reduce indoor humidity below 50% 5

For pet allergies:

• Remove pets from the home when feasible - this is the most effective measure 4
• If removal is not possible, exclude pets from bedrooms at minimum 4
• Note that benefits may take several weeks to months after pet removal due to persistent dander 5

Critical caveat: Standard allergen avoidance procedures used alone do not provide adequate symptom control and must be combined with pharmacotherapy 6. A comprehensive, multi-trigger approach including avoidance of irritants like cigarette smoke is necessary 6.

Immunotherapy: The Only Disease-Modifying Prevention

Allergen immunotherapy (subcutaneous or sublingual) should be offered to patients who have inadequate response to pharmacologic therapy with or without environmental controls, as it is the only treatment that can alter the natural history of allergic rhinitis and provide long-term prevention. 1, 4

• Immunotherapy can prevent development of new allergen sensitivities 4, 7
• It can reduce the risk of future asthma development, particularly in children 4, 7
• Benefits may persist for years after treatment discontinuation 7
• Both subcutaneous and sublingual routes are effective, with subcutaneous being more efficient and sublingual being safer 6, 8

Assessment and Management of Comorbidities

Clinicians must assess and document associated conditions that can worsen allergic rhinitis or be worsened by it, including asthma, atopic dermatitis, sleep-disordered breathing, conjunctivitis, rhinosinusitis, and otitis media. 1, 4

• Over 50% of patients with asthma have allergic rhinitis 4
• Treatment of allergic rhinitis with intranasal corticosteroids improves asthma control and reduces bronchial hyperreactivity 4, 7

Combination Therapy for Inadequate Response

For patients with inadequate response to intranasal corticosteroid monotherapy, combination therapy with intranasal antihistamine should be offered, particularly for moderate to severe symptoms. 4, 7

• The combination of intranasal corticosteroid plus intranasal antihistamine provides greater efficacy than either agent alone 1, 4
• This combination acts more rapidly than either drug used alone 6

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Critical Pitfalls to Avoid

Do not use oral leukotriene receptor antagonists (such as montelukast) as primary prevention therapy - they are significantly less efficacious than intranasal corticosteroids and should not be offered as first-line treatment 1, 4

Avoid prolonged use of intranasal decongestants beyond 10 days - this leads to rhinitis medicamentosa (rebound congestion) that worsens the underlying condition 4, 7

Do not use oral or parenteral corticosteroids for routine prevention - chronic use is inappropriate due to significant long-term adverse effects and should be reserved only for rare patients with severe intractable symptoms unresponsive to all other treatments 1, 4, 7

Do not rely on allergen avoidance alone - environmental control measures for indoor allergens have limited efficacy when used as monotherapy and must be combined with pharmacologic treatment 1, 6