Risk Factors for Allergic Rhinitis
The primary risk factors for allergic rhinitis include family history of atopy, elevated serum IgE levels in early childhood, higher socioeconomic status, and positive allergy skin prick tests. 1
Genetic and Early Life Risk Factors
Allergic rhinitis has a strong genetic component, with several key risk factors identified:
- Family history of atopy: Children with a bilateral family history (both parents) have a higher risk than those with unilateral family history and typically develop symptoms at a younger age 1
- Elevated serum IgE: Levels >100 IU/mL before age 6 years significantly increase risk 1
- Sex differences: More common in boys during childhood, but in adulthood the prevalence becomes equal or slightly favors women 1
- Birth order: More likely in first-born children 1
Environmental Risk Factors
Environmental exposures play a crucial role in allergic rhinitis development:
- Aeroallergen exposure: The primary trigger for allergic rhinitis, with sensitization potentially occurring as early as 6 months to 2 years of life 1
- Tobacco smoke exposure: Exposure to >20 cigarettes per day has been associated with increased risk of developing allergic rhinitis by age 1 1
- Urban living: Increased prevalence in polluted urban areas 1
- Socioeconomic status: Higher socioeconomic class is associated with greater risk 1
Controversial Risk Factors
Several factors show mixed evidence regarding their impact on allergic rhinitis development:
- Early childhood infections: The "hygiene hypothesis" suggests early exposure to infections might reduce atopy by redirecting the immune system away from allergic responses, but evidence is conflicting 1
- Animal exposure in early infancy: Some studies show cat exposure in early infancy may reduce atopy and asthma, while others show either no effect or increased allergic disease 1
- Month of birth: Some evidence suggests this may influence risk of pollen and dust mite sensitization, particularly in childhood, but not all studies agree 1
Progression and Timing of Sensitization
Understanding the timeline of allergic rhinitis development is important:
- Aeroallergen sensitization rarely begins before 6 months of age but may start between 6 months and 2 years 1
- Infants from atopic families are more frequently sensitized to pollen allergens than indoor allergens in the first year of life 1
- Seasonal allergic rhinitis typically develops between 2-7 years of age, as two seasons of exposure are generally required for sensitization 1
- Allergic rhinitis develops before age 20 in approximately 80% of cases 1
Clinical Implications
The identification of risk factors has important clinical implications:
- Early identification of high-risk individuals allows for potential preventive interventions
- Understanding that allergic rhinitis is a risk factor for asthma development, with approximately 1 in 10 patients with allergic rhinitis developing asthma 2
- Recognition that allergic rhinitis and asthma share common pathophysiological mechanisms as part of a "united airway" concept 1
By identifying these risk factors early, clinicians can better monitor high-risk patients and potentially implement strategies to reduce the development or severity of allergic rhinitis and its complications.