Of all the causes of allergies, pollen is one of the most widespread. Trees, weeds, and grasses produce pollen in large amounts for seed production. These pollens are dispersed by the wind, and many never reach the intended targets. Instead, they are inhaled through the nose and throat. Different plants release their pollen at different times of the year, so the timing of hay fever symptoms varies from person to person, depending on which plants provoke a response.
For people with hay fever, inhaled pollen grains are identified by the body as foreign invaders. This is probably due to a dysfunction in the immune system. The mast cells of the immune system act as storage containers for highly reactive chemical granules, including histamine. Allergens trigger a release of these granules, and the mast cells spill their chemicals into neighboring blood vessels and nerve cells. Histamine dilates the blood vessels, causing fluids to escape into surrounding tissues. This results in swelling, pooling of fluid in the tissues, and redness of the nose and eyes. Histamine also stimulates pain receptors, and causes the itchiness and discomfort of the nose, eyes, and throat that are common hay fever symptoms.
Inflammation of the nose, or rhinitis, is the major symptom of hay fever. Inflammation causes itching, sneezing, runny nose, redness, and tenderness. Swelling of the sinuses can constrict the eustachian tube that connects the inner ear to the throat, causing a feeling of congestion and popping in the ears. Mucus from the sinuses may run down the back of the throat, leading to throat irritation and redness. Seasonal fatigue and sinus headaches may also be indications of hay fever, as well as respiratory congestion and a decreased sense of smell. Severe allergies can lead to dark circles under the eyes, puffy eyelids, and creases under the eyes. Characteristically, children with hay fever may push their noses upward with the palm of their hand or twitch their noses to clear the congestion.
Virtually any type of tree or grass may cause hay fever, although plants with showy flowers usually produce a sticky pollen that is much less likely to become airborne. Among North American plants, weeds are the most prolific producers of allergenic pollen. Ragweed is the major culprit, but other plant pollens that routinely affect hay fever sufferers include sagebrush, lamb's quarter, Russian thistle, and English plantain. Grasses include timothy grass, Kentucky bluegrass, Johnson grass, Bermuda grass, redtop grass, orchard grass, and sweet vernal grass. Trees that produce allergenic pollen include oak, ash, elm, hickory, pecan, box elder, and mountain cedar.
Patience Paradox, Teresa G. Odle, The Gale Group Inc., Gale, Detroit,