Allergies caused by substances found in the air are often separated into seasonal or year-round allergies.
Year-round allergies are usually caused by substances found indoors, such as dust mites, cockroaches, or animal dander. Year-round allergies do not have a season. People with year-round allergies have symptoms that occur for more than two hours per day and for more than nine months of the year.
Seasonal allergies, on the other hand, are usually caused by allergens found outdoors, including pollen from trees, grasses and weeds along with spores from fungi and mold.
Many people think of spring or fall as allergy season. But there are actually many allergy seasons, depending on what you are allergic to, where you live, and how much of that substance is in the air.
Every year microscopic particles, known as pollen, are released into the air by different types of weeds, grasses, and trees.
Everyone breathes in pollen. For most people, it's harmless and your body gets rid of it easily. But for millions of Americans, pollen causes an allergic reaction.
Each plant has a pollinating period that is more or less the same from year to year, whether it be during the spring, summer, or fall. Trees are usually the first to pollinate, followed by grasses, then weeds. A person will have symptoms based on when the pollen grains to which they are allergic are in the air.
Location also plays a roll on when specific pollens are released. For example, in the Southeast or Southwest, the peak tree pollen period can begin as early as mid-January or February. In the Northeast, tree pollen levels may not become high until April.
The length of specific pollen periods can also vary by location. Peak pollen periods in the Northwest for grasses may stretch for six months, from May through October. In the Midwest, peak pollen periods for grasses may be as short as three months, from May through July.
Pollen counts are used to measure how much pollen is in the air over a certain area. They are often separated into absent, low, moderate, high, and very high. A pollen count can represent the concentration of all the pollen, or of one particular category, like weeds, or even type, like ragweed. The pollen count can be useful as a general guide for when it may be wise to stay indoors and avoid contact with the pollen.