The signs and symptoms of pollen allergy are familiar to many:

*Sneezing, the most common, may be accompanied by a runny or clogged nose

*Itching eyes, nose, and throat

*Allergic shiners (dark circles under the eyes caused by restricted blood flow near the sinuses)

*The "allergic salute" (in a child, persistent upward rubbing of the nose that causes a crease mark on the nose)

*Watering eyes

*Conjunctivitis (an inflammation of the membrane that lines the eyelids, causing red-rimmed eyes).

In people who are not allergic to pollen, the mucus in the nasal passages simply moves these foreign particles to the throat, where they are swallowed or coughed out. But something different happens to a pollen-sensitive person.
As soon as the allergy-causing pollen lands on the mucous membranes of the nose, a chain reaction occurs that leads the mast cells in these tissues to release histamine. This powerful chemical dilates the many small blood vessels in the nose. Fluids escape through these expanded vessel walls, which causes the nasal passages to swell and results in nasal congestion.

Histamine can also cause itching, irritation, and excess mucus production. Other chemicals, including prostaglandins and leukotrienes, also contribute to allergic symptoms.

Some people with pollen allergy develop asthma, a serious respiratory condition. While asthma may recur each year during pollen season, it can eventually become chronic. The symptoms of asthma include coughing, wheezing, shortness of breath due to a narrowing of the bronchial passages, and excess mucus production. Asthma can be disabling and can sometimes be fatal. If wheezing an shortness of breath accompany the hay fever symptoms, it is a signal that the bronchial tubes also have become, involved indicating the need for medical attention.