The pollen and spore production cycles of certain plants and molds create allergies in season. Seasonal allergic rhinitis, or hay fever, is a reaction to one of these. The Cleveland Clinic reports that flowering plants are the least likely to cause allergy symptoms. Their large, heavy pollen spores are insect-borne, rather than airborne. The lighter, more profuse pollens of grasses, trees and weeds, which travel on air currents in seasonal patterns, are most likely to trigger allergic rhinitis.
Tree Pollen Allergy
Some trees produce seeds and cones that contain tiny grains of pollen that are light enough to be transported for miles through the air. These granules are easily ingested by the human body during breathing, and therefore produce respiratory allergy symptoms, usually between February and May. Sneezing, nasal congestion and itchy eyes are common results of allergic reactions to tree pollens, as well as other hay fever allergens. According to the National Institutes of Health (NIH), fewer than 1 percent of all trees are known to cause allergic rhinitis. Those that do include alder, cedar, pecan, poplar and date palm. Tree allergies depend upon geographic location and seasonal factors.
Grass Pollen Allergy
Most allergy symptoms caused by airborne grass pollens develop between May and August, depending on where you live. Similar in physical qualities to tree pollens, grass pollens can be ingested at any time. Environmental grass pollen levels, however, may change by time of day or temperature, or with rainfall. If you have hay fever brought on by grass allergies, you can manage it by following pollen count reports. The Cleveland Clinic says the list of allergenic grasses includes fescue, a popular ornamental grass, as well as timothy, orchard, Kentucky blue, perennial rye and salt grasses.
Ragweed Allergy
Ragweed pollen is the most common cause of seasonal allergic rhinitis, the University of Maryland Medical Center says. Plants that are related to it, such as feverfew, dog fennel and chamomile, can also cause allergic reactions in some people. Other weed families, including sagebrush, lamb’s quarters and goosefoot, produce known allergens as well. Allergic reactions to these types of pollens are most prevalent in September but may occur from August through November.
Leaf Mold Allergy
You can get an allergic reaction to the spores of fungi, most commonly leaf mold, whenever decaying leaves litter the ground. Seasonal mold allergy symptoms can arise when temperatures are conducive to spore growth, generally March through November, the Cleveland Clinic says.
