Researchers estimate that pollen from flowering plants and grasses causes seasonal allergies in 35 million Americans.
Flowering plants have both male and female anatomies. Pollen is a collection of pollen grains, which are the tiny, egg-shaped male cells of flowering plants. Just a pinch of pollen contains thousands of pollen grains. Pollen grains are microscopic (about 15-100 microns).
Depending on the specific plant, the pollen is either released into the air or carried by insects to the female part of another plant. Plants, such as grasses and low-growing weeds (like ragweed), have airborne pollen, while plants with bright flowers (like roses) have waxy pollens that are carried from plant to plant by insects (like bees).
Airborne pollens are responsible for causing allergy symptoms, such as runny nose, itchy eyes, nasal congestion, and sneezing. Pollen is responsible for most cases of hay fever, which is also called allergic rhinitis. This allergic condition is characterized by a collection of allergic symptoms, predominantly in the nose and eyes, which occur after airborne pollen is inhaled. According to the American Lung Association, an estimated 26.1 million Americans suffer from hay fever symptoms each year. These allergies are seasonal because they occur when the allergy-causing plants are in bloom.
Since each type of plant has unique pollen, some pollen is more likely to cause allergies than others. The main physical features that distinguish one type of pollen from another include shape, size, and ornamentation of the outer wall.
Allergy symptoms are most common during the spring and summer months. One of the most common allergy-causing plants in the United States is ragweed.
Wind-pollinated plants like ragweed produce large quantities of pollen to ensure that some of it reaches the right target.
Pollen counts measure the amount of airborne pollen that is present in the air. Pollen counts are reported as number of pollen grains per cubic meter of air. When pollen counts are high, allergic individuals can take extra precautions to avoid exposure by limiting the amount of time spent outdoors, keeping the windows closed, and/or regularly washing the hands to remove pollen.
Pollen allergies may also be treated with medications, such as antihistamines, nasal corticosteroid sprays, and leukotriene receptor antagonists. Decongestants may also help treat nasal congestion (stuffy nose) that is often associated with pollen allergies.
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Pollen counts measure the amount of airborne pollens that are present in the air. Several methods can be used to generate pollen counts. Pollen counts are reported as pollen grains per cubic meter of air. Certified aeroallergen counters at many universities, medical centers, and clinics provide these counts on a volunteer basis.
For instance, the American Academy of Allergy, Asthma & Immunology (AAAAI) has a network of pollen counters across the United States. Certified pollen counters use specialized air-sampling equipment to capture airborne pollens.