Outdoor Allergens and Pollens

Seasonal allergic rhinitis, often referred to as "hay fever," affects more than 35 million people in the United States. These seasonal allergies are caused by substances called allergens. Airborne pollens and mold spores are outdoor allergens that commonly trigger symptoms during the spring and fall. During these times, seasonal allergic rhinitis sufferers experience increased symptoms-sneezing, congestion, a runny nose, and itchiness in the nose, roof of the mouth, throat, eyes and ears-depending on where they live in the country and the exact allergen to which they are allergic.

Pollens are the tiny, egg-shaped male cells of flowering plants. These microscopic, powdery granules are necessary for plant fertilization. The average pollen particle is less than the width of an average human hair. Pollens from plants with bright flowers, such as roses, usually do not trigger allergies. These large, waxy pollens are carried from plant to plant by bees and other insects. On the other hand, many trees, grasses and low-growing weeds have small, light, dry pollens that are well-suited for dissemination by wind currents. These are the pollens that trigger allergy symptoms.

Seasonal allergic rhinitis in the early spring is often triggered by the pollens of such trees as oak, western red cedar, elm, birch, ash, hickory, poplar, sycamore, maple, cypress and walnut. In the late spring and early summer, pollinating grasses-including timothy, bermuda, orchard, sweet vernal, red top and some blue grasses-often trigger symptoms. In addition to ragweed-the pollen most responsible for late summer and fall hay fever in much of North America-other weeds can trigger allergic rhinitis symptoms. These weeds include sagebrush, pigweed, tumbleweed, Russian thistle and cockleweed.

Each plant has a period of pollination that does not vary greatly from year to year. However, weather conditions can affect the amount of pollen in the air at any given time. The pollinating season starts later in the spring the further north one goes. Depending on where you live in the United States, the pollen season can begin as early as January (in the southern states).

Generally, the pollen season lasts from February or March through October. Trees pollinate earliest, from late February through May, although this may fluctuate in different locations-starting in April in the northern United States to as early as January in the south. Grasses follow next in the cycle, beginning pollination in May and continuing until mid-July. Weeds usually pollinate in late summer and early fall.

Molds Molds are microscopic fungi-related to mushrooms-but without stems, roots or leaves. Their spores float in the air like pollen, and are present throughout the year in many states. Unlike pollens, molds do not have a specific season, but are affected by weather conditions such as wind, rain or temperature. Outdoor mold spores begin to appear after a spring thaw and reach their peak in July in warmer states and October in the colder states. Molds can be found all year long outdoors in the South and on the West coast. Common airborne molds include alternaria, cladosporium and aspergillus. Molds are present in almost every possible habitat. Outdoors, they can be found in soil, vegetation and rotting wood. Molds can also be found indoors in attics, basements, bathrooms, refrigerators and other food storage areas, garbage containers, carpets and upholstery.

Pollen and mold counts measure the amount of airborne allergens present in the air. Counts are compiled by a variety of methods. Pollen and mold spore counts can be determined daily, and are reported as grains per cubic meter of air. Certified aeroallergen counters at many universities, medical centers and clinics provide these counts on a volunteer basis. The National Allergy BureauT (NABT) is the nation's only pollen and mold counting network certified by the AAAAI. As a free service to the public, the NAB compiles pollen and mold counts from certified stations across the nation and reports them to the media three times each week. These counts are also available on the NAB page of the AAAAI's Web site, www.aaaai.org. Interpretation of pollen and mold counts and their relationship to symptoms is complex. Sampling techniques such as the type of device used and its location within the community can affect counts. While many patients develop symptoms when pollen counts are 20-100 grains per cubic meter, one's symptoms may also be affected by recent exposure to other allergens, the intensity of pollen exposure, and individual sensitivity. Pollen counts reported to the public are generally taken the preceding one to three days, and may vary widely from day to day during a season. Overall, the use of pollen counts in predicting symptom severity in a given individual is somewhat limited.

Weather can influence hay fever symptoms. Allergy symptoms are often minimal on days that are rainy, cloudy or windless, because pollen does not move about during these conditions. Hot, dry and windy weather signals greater pollen and mold distribution and thus, increased allergy symptoms.

If you are allergic to plants in your area, you may believe that moving to another area of the country with different plants will help to lessen your symptoms. However, many pollens (especially grasses) and molds are common to most plant zones in the United States. Additionally, other related plants can also trigger the same symptoms. Many who move to a new region to escape their allergies find that they acquire allergies to new airborne allergens prevalent in their area within one to two years. Therefore, moving to another part of the country to escape allergies is often ultimately disappointing, and not recommended. Appropriate treatment-not escape-is the best method for coping with your allergies.

If your seasonal allergy symptoms are making you miserable, see your allergist/immunologist, who will take a thorough history and conduct tests, if needed, to determine exactly which pollens or molds are triggering your symptoms. He or she will help you determine when these airborne allergens are most prevalent in your area. To lessen your symptoms, your allergist/immunologist may also prescribe an allergy nose spray, non-sedating antihistamine, decongestant or other medications. If your symptoms continue or if you have them for many months of the year, your allergist may also recommend immunotherapy treatment. This treatment involves receiving injections or sublingual tablets as determined by your allergist/immunologist-over a period of three to five years. This treatment helps your immune system to become more and more resistant to the specific allergen, and lessens your symptoms as well as the need for future medications.