About 10 percent of Americans have a pollen allergy, also known as allergic rhinitis. Pollen allergies are the result of a problem your immune system has with certain airborne substances that are released by trees and flowers. Instead of allowing you to enjoy the spring and summer, your body reacts to the pollination activity during these seasons by thinking you're under attack. When you inhale any of the pollens you're allergic to, your immune system sends out an antibody called immunoglobulin E to neutralize the allergen. In turn, the antibody triggers a bunch of chemicals to wage the war on its behalf. You notice the symptoms of the fight, particularly those caused by the chemical histamine. The combination of these pollen allergy symptoms is often called "hay fever."
Despite the word "fever," hay fever is more commonly experienced through a runny nose, itchy eyes, congestion and sneezing than through a fever. Hay fever got its name because the people who suffer from pollen allergies tend to feel unwell during pollination season. However, hay fever doesn't actually involve a fever. You can tell the difference between hay fever and a cold because the mucous associated with a cold is thicker than with allergies; in addition, colds are sometimes accompanied by hoarseness and fever. Plus, they go away a lot faster than allergies do.
Typically, trees start to pollinate in the early spring and grasses start in late spring. Ragweed begins to pollinate in late summer. Depending on what type of pollen you're allergic to, your symptoms will be worse at different times of year. The local weather report often includes a pollen count to warn hay fever sufferers how bad their allergies will be that day. Pollen counts are higher when it's warm and dry than when it's raining or cold.