Hay Fever (Allergic Rhinitis): Not Contagious, Not Spread by Saliva

Hay fever (seasonal allergic rhinitis) is an IgE-mediated hypersensitivity to airborne allergens (pollen, mold spores, dust mites, animal dander). It is NOT contagious.

Transmission

• Cannot be transmitted via saliva, respiratory droplets, touch, fomites, or sexual contact.
• No infectious agent involved — it's an immune misdirection.

Pathophysiology

1. Sensitization: Allergen → dendritic cell → Th2 → IgE production.
2. Re-exposure: Allergen cross-links IgE on mast cells/basophils → degranulation.
3. Mediators: Histamine, leukotrienes, prostaglandins → sneezing, rhinorrhea, congestion, itching, conjunctivitis.

Management

• Avoidance (pollen counts, HEPA filters, encasings)
• Intranasal corticosteroids (first-line)
• Second-gen antihistamines (cetirizine, fexofenadine, loratadine)
• Leukotriene receptor antagonists (montelukast)
• Immunotherapy (SCIT/SLIT) for long-term modification

You cannot "catch" allergies from someone else — but you can share genetic predisposition and environment.