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  Outdoor Allergens

Seasonal allergic rhinitis, often referred to as "hay fever," affects about 10~20% of population throughout the world. 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. In the temperate region, 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 - other weeds can trigger allergic rhinitis symptoms. These weeds include sagebrush, pigweed, Japanese hop and goosefoot. 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 in South Northern Asian countries such as Korea, China, and Japan. The pollinating season starts later in the spring. Tree 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 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.

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

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. Some countries like Korea have national aeroallergen college counters throughout the country and report the data weekly to the public.

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.

Effects of weather and location

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, 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/immunologist may also recommend immunotherapy treatment, also called allergy vaccinations or shots. This treatment involves receiving injections periodically - 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.

Tips for those who have allergen to pollen and mold

  • What you have to
      1. Keep windows closed at night to prevent pollens or molds from drifting into your home. Instead, if needed, use air conditioning, which cleans, cools, and dries the air.
      2. Minimize early morning activity when pollen is usually emitted-between 5-10 a.m.
      3. Keep your car windows closed when traveling.
      4. Try to stay indoors when the pollen count or humidity is reported to be high, and on windy days when dust and pollen are blown about.
      5. Take medications prescribed by your doctor
      regularly, in the recommended dosage.

  • What you don't have to
      1. Take more medication than recommended in an attempt to lessen your symptoms.
      2. Mow lawns or be around freshly cut grass; mowing stirs up pollens and molds.
      3. Rake leaves, as this also stirs up molds.
      4. Hang sheets or clothing out to dry. Pollens and molds may collect in them.
      5. Grow too many, or overwater, indoor plants because wet soil encourages mold growth.

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