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The Eight Allergy Zones In The United States

Eight Allergy Zones of the United States

Allergies are a common condition not only in the United States, but all over the world. According to the Centers for Disease Control and Prevention, more than 50 million Americans suffer from allergies each year. Allergies are defined as a hypersensitivity disorder of the immune system that occurs when the body’s immune system overreacts to what is normally a harmless substance. The allergen may irritate four of the five individual's senses – smell, sight, taste and touch – causing inflammation, disability and in severe cases, even death. In order to avoid an allergic reaction, it is necessary to find out what you're allergic to and then avoid exposure to that allergen as much as possible. However, this is not such an easy task as it may sounds, as each part of the U.S has different varieties of weeds, trees and grasses. This is where the eight (8) allergy zones come into play. Each zone is a different region of the United States, designed to help better identify the cause of a person's allergic reaction.

The Different Zones

The eight allergy zones in the continental United States are defined as the Pacific, Mountain, Desert, Plains, Southwest, Great Lakes, South, and Northeast. Each zone has a distinctive ecosystem with unique varieties of common allergens present, as well as different allergy seasons. Factors including average temperature, humidity, elevation, precipitation, among others, are used to create the divisions and the common allergens found are fairly similar throughout each zone. Some of the most common allergens found in most of these regions include a variety of grasses, trees (such as oak and cedar), and ragweed.

Using Allergy Zones

Allergy zones were created in order to be able to better identify the triggers of individuals' seasonal allergies. The zone map can be used as a reference to get more information on what is currently spreading pollen in your area and compare that against what you're exposed to on a daily basis. Doctors will also use the allergy zone chart to determine which allergens to look for in an allergy skin test, which is used to determine the cause of your allergies. This test helps find the most effective treatments to effectively combat an individual's allergy symptoms. Zones do have allergens in common, so if you move between zones and experience the same seasonal allergies, you're probably allergic to something that is common in both zones.

The Most Common Outdoor Allergens in the United States


The Southeast region of the United States is home to particular trees, weeds and grasses that cause more allergies than others, some blooming year round and others being active in specific months. One of the top year-round allergens is Bermuda grass which produces allergic reactions at virtually anytime of the year. Tree allergens are strongest and in full bloom from February and May - the main allergen culprits being oak, pecan and cedar. June through November, weed allergens are most active with nettle and ragweed being the most common.


In the Southwest, the most prevalent grass allergy comes from redtop grass which is a perennial grass that blooms from May through July. This region is also home to tree allergens mainly from oak trees, but also from cedar and elm. July through September, chenopod blooms and causes the majority of weed allergies.


If you're visiting or living in the Northeast, there are specific trees, weeds and grasses to be aware of. Orchard and redtop bloom from May through August and are at the top of the list for grass allergies. If you're allergic to tree pollen, oak, pine and birch are in high bloom from February through June. From August through October, ragweed and stinging nettle make weed allergies worse.


One of the most common grasses in the Midwest that is likely to give you allergies is called Brome. It is a perennial grass that grows in the spring and blooms through July. Elder, elm and maple trees are the main culprits for tree allergies and bloom from early spring through early summer (March to June).


There are several common causes of allergies on the West coast. Grasses such as sweet vernal can cause severe allergies from March through November. From February though June, trees such as walnut and cedar are top allergen producers. Weed allergies are the worst from April through November with iodine bush and pigweed being the leading cause of seasonal allergies from weeds.

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