Share on Pinterest
Getty Images/raquel arocena torres

Hundreds of species of plants release their pollen into the air every year, causing allergic reactions in many people. But only a relatively small number of plants are responsible for most of the itching, sneezing, and watery eyes associated with hay fever.

Certain pollens — such as ragweed — can even survive through the winter and play havoc with immune systems year-round. All of that pollen has created a booming market for antihistamine and decongestant makers, but has left millions of people with allergies begging for relief.

Certain plants are worse than others. Here are the top allergens found in North America:

  • ragweed: throughout
    North America
  • mountain
    cedar: Arkansas, Missouri, Oklahoma, and Texas
  • ryegrass: throughout
    North America
  • maple:
    throughout North America
  • elm:
    throughout most of North America
  • mulberry:
    throughout the United States (but rare in Florida and desert regions of the
  • pecan: Southern states in the U.S.
  • oak:
    throughout North America
  • pigweed/tumbleweed: throughout
    North America
  • Arizona
    cypress: Southwestern United States

Late winter and early spring is tree allergy season. Some trees start releasing their pollen as early as January, while others continue their onslaught into summer. Thankfully, only about 100 of the more than 50,000 tree species cause allergies.

Tree pollens are dry and lightweight, so they can travel great distances in the wind. Some of the worst tree allergens include:

  • alder
  • ash
  • beech
  • birch
  • box elder
  • cedar
  • cottonwood
  • date palm
  • elm
  • mulberry
  • hickory
  • juniper
  • oak
  • pecan
  • Phoenix palm
  • red maple
  • silver maple
  • sycamore
  • walnut
  • willow

Most people with allergies are only allergic to one type of tree, but it’s possible to experience an allergic reaction as a result of a cross-reaction. A cross-reaction happens when the proteins in one allergen (usually a pollen) are very similar to the proteins in another (usually a food).

One common example of a cross-reaction is birch pollen and apples. Talk to your doctor if you notice allergy symptoms that develop when you’re exposed to certain pollens or foods. You may experience itching or tingling of the mouth when eating a particular food. An allergy test can confirm a cross-reaction.

Grass allergy season starts in late spring and summer. There are thousands of species of grass in North America, but only a handful cause serious allergic reactions.

People with grass allergies must take extra care when doing yard work — especially when mowing the lawn. Wear a mask when doing yard work. Keep your grass cut short, or replace your grass with a ground cover that produces less pollen. Ground covers include bunch, dichondra, and Irish moss.

Also, don’t wear outdoor clothes that may have collected pollen inside the house, and avoid drying clothes outside. You should replace your home air filters often to avoid collection of pollen. Grass is easily tracked indoors, so vacuuming may also help relieve symptoms. The most common grass allergens include:

  • Bermuda grass
  • Johnson grass
  • Kentucky bluegrass
  • orchard grass
  • rye grass
  • sweet vernal grass
  • Timothy grass

Late summer and fall is the season for weed allergies, with pollen levels usually peaking in mid-September. Pollen counts for weeds are highest in the morning, usually between 5 a.m. and 10 a.m. Weed pollens are the most prolific allergens of all. A single ragweed plant, for instance, can produce a billion pollen grains in a season. Wind-carried grains can also travel for hundreds of miles. Weeds responsible for the most allergies include:

  • English plantain
  • lamb’s quarters
  • ragweed (which affects nearly one in five
  • redroot pigweed
  • sagebrush
  • tumbleweed (Russian thistle)

The American Academy of Allergy, Asthma, and Immunology publishes pollen counts for individual cities in America. You can take extra precautions when you know that counts for your allergen are high, such as limiting your time outdoors.

Avoiding allergy triggers and using over the counter medications can help you manage your allergy symptoms. Call your doctor if you can’t avoid your allergy triggers, or if over the counter medications aren’t working for you. Your doctor can refer you to an allergy specialist who will help identify your allergy triggers and create a suitable treatment plan for you.