Pollen allergy is a type of seasonal allergic rhinitis that typically occurs in the spring, summer, and fall when pollen grains are released from trees, weeds, and grasses. Of all the different types of allergies, pollen is one of the most common. Although preventive measures can be taken for other types of allergies -- such as foods, animals, and medicines -- this type is more difficult to prevent and avoid because there is no easy way to avoid airborne pollen.
Each spring, summer, and fall, tiny pollen grains are released from trees, weeds, and grasses. These grains hitch rides on currents of air. Although the mission of pollen is to fertilize parts of other plants, many never reach their targets. Instead, pollen enters human noses and throats, triggering a type of seasonal allergic rhinitis called pollen allergy. Many people know this as hay fever.
Of all the things that can cause allergies, pollen is one of the most common. Many of the foods, medicines, or animals that cause allergies can be avoided to a great extent. Even insects and household dust are escapable. However, short of staying indoors with the windows closed when the pollen count is high (and even that may not help), there is no easy way to avoid airborne pollen.
Plants produce tiny -- too tiny to see with the naked eye -- round or oval pollen grains to reproduce. In some species, the plant uses the pollen from its own flowers to fertilize itself. Other types must be cross-pollinated. Cross-pollination means that for fertilization to take place and seeds to form, pollen must be transferred from the flower of one plant to that of another of the same species. Insects do this job for certain flowering plants, while other plants rely on wind for transport.
The types of pollen that most commonly cause allergic reactions are produced by the plain-looking plants (trees, grasses, and weeds) that do not have showy flowers. These plants make small, light, dry pollen grains that are custom-made for wind transport.
Amazingly, scientists have collected samples of ragweed pollen 400 miles out at sea and 2 miles high in the air. Because airborne pollen can drift for many miles, it does little good to rid an area of an offending plant. In addition, most allergenic pollen comes from plants that produce it in huge quantities. For example, a single ragweed plant can generate a million grains of pollen a day.