There are two main types of allergic rhinitis or nasal allergies. Those that produce allergy symptoms year round are considered perennial, and those that trigger attacks in concert with plant pollen and spore cycles are considered seasonal.
Once patients determine whether they have single or multiple seasonal or perennial allergies, they may be able to identify the cause of allergic reactions. According to the University of Maryland Medical Center, allergens that are ingested by breathing are most likely to cause sneezing, congestion and other nasal symptoms.
Grass, Tree and Ragweed Pollen
Pollen from plants that are abundant and light enough to be transported on air are responsible for the majority of seasonal allergic rhinitis conditions. Among these, the UM Medical Center lists fall ragweed pollen as the leading cause of nasal allergic reactions.
Spring tree pollen produced by alder, elm, cedar, sycamore and other trees growing in the United States is another airborne allergen source. Summer grass pollens that may set off allergy symptoms include Bermuda, Johnson, Kentucky blue, redtop, timothy and fescue grasses, as recorded by the Cleveland Clinic.
Leaf Mold Spores
Another category of plant allergens that causes seasonal allergy symptoms are produced by fungi that grow on decaying leaves. Commonly known as leaf mold, these fungi produce tiny spores. Once airborne, they can be ingested by humans and create allergic reactions in some people. The Cleveland Clinic notes that nasal problems caused by leaf mold spores can arise anytime between March and November when leaves are on the ground. Levels of leaf mold allergens are usually highest, however, in the summertime. It may be difficult to diagnose fungal seasonal allergic rhinitis. Patients can be sensitive to more than one type of mold, which may provoke different degrees of symptoms over a longer period of time.
Household Dust
The National Institutes of Health reports that household dust is a major source of allergens that cause perennial allergic rhinitis. Certain components of dust, rather than dust itself, is what creates perennial allergy symptoms. Household dust is composed of small organic particles and the mites that feed on them. These household mites are small enough to become airborne and for humans to ingest, and some people are allergic to them. Dust also contains common allergens such as mold and dog and cat dander, which can trigger allergic reactions in some people. The NIH notes that perennial symptoms often increase in wintertime, when indoor environmental allergen levels are higher due to less air ventilation.
