What is allergic rhinitis (hayfever)?

What is Hayfever (Allergic Rhinitis)?

Hayfever, or allergic rhinitis (AR), is a disease caused by an IgE-mediated inflammatory response of the nasal mucous membranes after exposure to inhaled allergens, characterized by symptoms including rhinorrhea (nasal drainage), nasal congestion, nasal itching, and sneezing. 1

Definition and Prevalence

• Allergic rhinitis affects approximately 1 in 6 Americans (nearly 50 million individuals), making it the fifth most common chronic disease in the United States 1, 2
• It generates $2-5 billion in direct health expenditures annually and causes $2-4 billion in lost productivity through missed work and school days 1
• AR is more common in individuals with a family history of atopy, elevated serum IgE levels in early childhood, higher socioeconomic class, and positive allergy skin prick tests 3

Classification of Allergic Rhinitis

Allergic rhinitis can be classified in several ways:

1. By temporal pattern of allergen exposure: 1

   • Seasonal allergic rhinitis (SAR): Caused by seasonal aeroallergens like pollens
   • Perennial allergic rhinitis (PAR): Caused by year-round allergens like dust mites, mold, and animal dander
   • Episodic allergic rhinitis: Occurs with sporadic exposures to allergens not normally in the patient's environment (e.g., visiting a home with pets)

2. By frequency of symptoms: 1

   • Intermittent: Symptoms occur <4 days per week or <4 weeks per year
   • Persistent: Symptoms occur >4 days per week and >4 weeks per year

3. By severity of symptoms: 1

   • Mild to severe, based on impact on quality of life

Clinical Presentation

The primary symptoms of allergic rhinitis include: 1, 2

• Nasal congestion (stuffy nose)
• Rhinorrhea (runny nose)
• Sneezing
• Nasal itching
• Postnasal drip

Common physical examination findings include: 4

• Clear rhinorrhea
• Pale nasal mucosa
• Swollen nasal turbinates
• Watery eye discharge
• Conjunctival swelling
• Allergic shiners (dark circles under the eyes)

Pathophysiology

• AR occurs when disruption of the epithelial barrier allows allergens to penetrate the nasal mucosa, triggering an IgE-mediated inflammatory response 2
• The allergic response occurs in two phases: 5
  • Early phase: Occurs within minutes of allergen exposure, producing sneezing, itching, and clear rhinorrhea
  • Late phase: Occurs 4-8 hours after exposure, characterized by congestion, fatigue, and malaise

Associated Conditions and Complications

• AR is frequently associated with other conditions including asthma, eczema, chronic sinusitis, and both tension and migraine headaches 2
• Approximately 10% of patients with allergic rhinitis will develop asthma 4
• AR can significantly impair quality of life, sleep quality, and performance at work or school 6
• Mixed rhinitis (combined allergic and nonallergic rhinitis) is noted in approximately 44-87% of patients with allergic rhinitis 1

Diagnostic Approach

• Diagnosis is primarily clinical, based on history, physical examination, and presence of characteristic symptoms 4
• Serum or skin testing for specific allergens should be performed when there is inadequate response to empiric treatment, if diagnosis is uncertain, or to guide therapy 4
• The key to diagnosis is awareness of signs and symptoms, with confirmation through IgE antibody tests to detect specific allergens 5

Common Pitfalls in Diagnosis

• Failing to distinguish between allergic and non-allergic rhinitis, which have different risk profiles and treatment approaches 3
• Not recognizing mixed rhinitis, which affects a large percentage of patients with allergic rhinitis 3
• Difficulty differentiating perennial AR from sinusitis, respiratory infections, and vasomotor rhinitis 5

Understanding allergic rhinitis is essential for proper management, as appropriate classification by allergen exposure pattern, frequency, and severity allows for more targeted treatment approaches.