Hay fever refers to a seasonal allergic rhinitis condition that arises from the body’s abnormal response to seasonal pollen and other irritants. Contrary to some belief, trees, grasses and weeds are more likely to cause allergy symptoms than plants that produce flowers and fruits. The Cleveland Clinic explains that this is related to the size and weight of the plants’ pollen grains. Humans can most easily ingest light granules that disperse through the air, rather than the heavier types carried by insects. Symptoms include sneezing, itchy eyes and runny nose.
Ragweed Pollen Allergy
The most common sources of pollen allergens in North America are those in the ragweed family. According to the Asthma and Allergy Foundation of America, three-quarters of U.S. allergy patients get allergic rhinitis from ragweed pollen exposure. These individuals may have sensitivities to other types of hay fever as well. The profusion of pollen generated by ragweed—up to 1 billion grains—makes it very successful in raising environmental pollen counts. Ragweed grows mainly in the eastern region, while allergenic weeds with similar effects, such as sagebrush and lamb’s quarters, may be found throughout the country. Allergy symptoms will arise at various times depending on the geographic region, with ragweed-induced allergic rhinitis peaking in mid-September.
Tree Pollen Allergy
Some types of tree pollen do as much damage as ragweed in certain allergy patients. The majority of the U.S. experiences airborne tree pollens in late winter or early spring, but some warmer climates are hit as early as December. The National Institutes of Health note that extremely light tree pollens can travel very long distances, affecting patients in other regions.
Common hay fever-causing trees include alder, elm, walnut, cottonwood and trees in the cedar, juniper and cypress families. The NIH points out that in some species, only the male tree sets off allergy symptoms.
Grass Pollen Allergy
Grass represents another member of the small, light, airborne pollen producers that plague hay fever sufferers. The Cleveland Clinic lists timothy, fescue, Kentucky blue, sweet vernal, orchard and perennial rye grasses among the grasses that cause allergic rhinitis. Grass allergy symptoms arise in the summer when seed heads release their pollen grains into to the air. Like tree and ragweed pollens, temperature, humidity, precipitation and time of day affect the mobility of light grass pollens. Patient with these types of plant allergy are most susceptible to outdoor contact from 5 a.m. to 10 a.m., according to the NIH.
