Hay fever is the more common name for pollen allergies, and both fall under the category of allergic rhinitis. Hay fever is the result of an immune system malfunction wherein your body thinks that the pollen released by grass, trees and weeds is dangerous -- even though it isn't. When you breathe in allergenic pollen, your immune system responds by releasing an antibody called immunoglobulin E; it triggers mast cells to neutralize the invading pollen. The fight between your body and the pollen also produces chemicals; one of them, histamine, is responsible for most of your allergic symptoms.
The symptoms of hay fever in children are the same as the symptoms for an adult: runny nose, sneezing, itchy or watery eyes, itchy ears or scratchy throat. However, kids don't usually get hay fever before they turn three, and often, pollen allergies aren't noticeable until a child is around seven years old. To differentiate between hay fever, a cold and other allergies, pay attention to when symptoms occur. Hay fever is normally a problem from the spring to the late summer, when trees, grass and weeds pollinate. It can vary depending on your child's specific allergy. Hot, dry weather is worse for allergy sufferers, especially if there's a good breeze to blow the pollen around. Flowers aren't a problem for hay fever sufferers since their pollen is spread by insects, as opposed to by the air.
Although hay fever can be hard to differentiate from a cold, an important difference is duration: Colds last a week or two, but hay fever can last months. Plus, allergies don't produce a fever. So if your child has a fever, he probably isn't suffering from hay fever (despite the name). However, if his cold-like symptoms seem to relax a bit when he goes inside, it's a sign your child might have hay fever.