How allergies develop
Allergens develop in two phases.
Phase 1
First, your immune system responds to certain substances by creating antibodies called immunoglobulin E (IgE). This part is called sensitization.
Depending on what kind of allergy you have, such as pollen or food, these antibodies are localized in your airways — including your nose, mouth, throat, windpipe, and lungs — your gastrointestinal (GI) tract, and your skin.
Phase 2
If you’re exposed to that allergen again, your body releases inflammatory substances, including the chemical histamine. This causes blood vessels to dilate, mucus to form, skin to itch, and airway tissues to swell up.
This allergic reaction is meant to stop allergens from getting in and to fight off any irritation or infection that might be caused by the allergens that do get in. Essentially, you can think of allergies as an overreaction to those allergens.
From then on, your body responds similarly when it’s exposed to that allergen in the future. For mild airborne allergies, you might experience symptoms of puffy eyes, stuffy nose, and itchy throat. And for severe allergies, you might have hives, diarrhea, and trouble breathing.
