Allergies kick in when your immune system overreacts to normally harmless substances called allergens. Your body releases a chemical called histamine, and you start to experience a variety of symptoms.
ITCHY, WATERY EYES
Many allergens are airborne and come into direct contact with your eyes. That’s why people with allergies experience itchy, watery, teary eyes.
Your body’s reaction to histamine includes itchiness and swelling inside your nose and throat. As a result, your brain tells your chest to contract and you start sneezing.
When allergens enter your nose, the membrane swells and presses a fluid out of small blood vessels in your nasal passages – typically a thin, clear liquid.
ITCHY NOSE OR THROAT
Itchy nasal passages are also a reaction to a lot of histamine in your system.
If your allergies include upper respiratory symptoms – sneezing, itchy and stuffy nose – your sinuses may become swollen and blocked.