What Are Allergies?
In people with allergies, the immune system mistakes a substance that’s ordinarily harmless to most people (substances from pollen, mold, pet dander and dust mites) for something dangerous and attacks it. These normally harmless substances are called allergens.
What Causes Allergy Symptoms?
When you take a breath or rub your nose or eyes, allergens enter your body and your immune system triggers a hypersensitivity reaction. To get rid of the substance it thinks is harmful, your body undergoes various reactions and releases inflammatory mediators like histamine.
When the histamine binds to receptors on other cells in your body, it causes you to experience allergy symptoms, including runny nose, sneezing, itchy/watery eyes, itchy nose or throat, nasal congestion and sinus pressure.