Allergies happen when your body detects some kind of foreign substance, such as a pollen grain or pet dander, and activates an immune system response to fight it off.
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.
When allergies typically develop
Most people remember first getting allergy symptoms at a young age — about 1 in 5 kids have some kind of allergy or asthma. Many people outgrow their allergies by their 20s and 30s, as they become tolerant to their allergens, especially food allergens such as milk, eggs, and grains.
But it’s possible to develop an allergy at any point in your life. You may even become allergic to something that you had no allergy to before.
It isn’t clear why some allergies develop in adulthood, especially by one’s 20s or 30s.
Let’s get into how and why you can develop an allergy later in life, how you can treat a new allergy, and whether you can expect a new allergy or an existing one to go away with time.
