What causes seasonal allergies and how do they work?

Seasonal allergies are your body’s immune system accidentally attacking harmless things like pollen because it thinks they are dangerous invaders.

It starts when tiny, dust-like pollen grains float in the air from trees and grasses. Your eyes and nose catch these pollen grains and let them into your body. Normally, your immune system is a helpful security guard that ignores these harmless guests. But if you have allergies, your security guards are on high alert and mistake pollen for a scary invader like a virus or bacteria.

To fight the "fake" enemy, your body releases a chemical called histamine. Think of histamine like tiny bubbles popping under your skin. These bubbles make the walls of your blood vessels leaky so more defense troops can rush to the scene. This rushing causes swelling and itching in your nose and eyes.

The symptoms feel different because histamine does three things at once:

• It makes your nose run to wash away the pollen, like a hose spraying water.
• It makes you sneeze to blow the pollen out, like a sudden burst of air from a balloon letting go.
• It makes your eyes itch and water because the "bubbles" tickle the nerves there.

When the sun goes down or it rains, the pollen count drops, so fewer "invaders" are around, and you feel better. The next day, when the wind blows more pollen into your face, your security guards see them again and release more histamine bubbles, bringing back the sneezes and itches.