But for people who are allergic to these ordinary everyday things, these substances present more serious consequences. They set off a complicated chain reaction in which the body works hard to expel them. That's why your nose runs, your eyes water, you sneeze and cough. To the naked eye, it looks like plain powder or dust. But it's really the male fertilizing agent of plants.
Pollen relies on the wind to sweep it from one plant to the next.
It's because pollen is airborne that it poses such a problem for allergy sufferers. The first time you breathe in pollen, it makes its way to your nose and sets off your immune system. Your immune system decides pollen is dangerous, and makes a small amount of antibody to fight it. But the next time you breathe it in, and every time after that, your body remembers this foreign invader and manufactures lots of antibody to fight it off. Histamine encourages your tissues to secrete fluids and become irritated.