At what age do seasonal allergies typically start?

At What Age Do Seasonal Allergies Start?

Seasonal allergic rhinitis symptoms generally do not develop until 2 to 7 years of age, as at least two seasons of pollen exposure are typically required for sensitization to occur. 1

Timeline of Allergic Sensitization and Symptom Development

Early Sensitization Phase

• Aeroallergen sensitization rarely begins before 6 months of age but may start between 6 months and 2 years of life 1
• Infants born to atopic families are sensitized to pollen aeroallergens more frequently than to indoor aeroallergens in the first year of life 1
• Perennial allergic rhinitis may be present at a very early age, as sensitization to perennial allergens (dust mites, animals, cockroaches) may manifest several months after exposure 2, 3

Clinical Manifestation of Seasonal Allergies

• The typical age range for seasonal allergic rhinitis onset is 2 to 7 years 1, 2
• Two or more seasons of pollen exposure are generally needed for sensitization before symptoms become clinically manifest 2, 3, 4
• Children who develop seasonal allergic rhinitis in their second year of life are typically born in spring or early summer, ensuring at least two pollen seasons of exposure before symptom onset 4
• Prevalence and incidence of seasonal allergic rhinitis symptoms and sensitization are low during early childhood (<2%) and increase steadily with age 4

Important Clinical Context

Age-Related Patterns

• Allergic rhinitis develops before age 20 years in 80% of cases 1
• The prevalence of seasonal allergic rhinitis is higher in children and adolescents, whereas perennial allergic rhinitis has a higher prevalence in adults 1
• By age 7, approximately 15% of children will have developed seasonal allergic rhinitis 4

Risk Factors That May Influence Earlier Onset

• Children with a bilateral family history of atopy may develop symptoms more frequently and at a younger age than those with a unilateral family history 1
• Risk factors include: family history of atopy, serum IgE >100 IU/mL before age 6 years, higher socioeconomic class, and presence of positive allergy skin prick test 1
• Male sex increases risk (odds ratio 2.4), as does having atopic parents with allergic rhinitis themselves 4

Clinical Pitfalls to Avoid

Testing Considerations

• Allergy testing to seasonal allergens (trees, grasses, weeds) should be conducted after age 2 or 3 years, as two seasons of exposure are needed for sensitization 3
• Testing before this age may yield false negatives and lead to missed diagnoses or inappropriate reassurance

Atopic March Awareness

• Children with early childhood eczema have a 57.6% likelihood of developing allergic rhinitis, with risk related to severity of dermatitis 2
• Children with atopic dermatitis should be regularly assessed for symptoms of allergic rhinitis as they age, particularly after age 2 years 2

Distinguishing Seasonal from Perennial Rhinitis

• While seasonal allergies typically start at 2-7 years, perennial allergic rhinitis from indoor allergens can present earlier, even in infancy 2, 3
• The distinction is clinically important for treatment planning and allergen avoidance strategies 1