From the WebMD Archives

Aug. 21, 2019 -- People who have allergies may be in for a rough ragweed season this summer and fall, thanks to hotter and wetter weather nationwide.

The flowering weed produces a type of sneeze-inducing pollen known to cause hay fever, a condition that affects as many as 23 million people in the United States, according to the American College of Allergy, Asthma and Immunology (ACAAI).

Ragweed has run amok across the country over the past few years, according to allergists. The culprit is extreme weather -- high temperatures and heavy rain -- that creates the perfect environment for ragweed-producing plants to grow. As a result, the allergy season becomes longer and more brutal.

“The last few years, the trend has been for higher ragweed counts, and part of that is the longer season and general climate warming,” says Stanley Fineman, MD, an allergist and former president of the ACAAI. “We know that plants like water and heat, and it's been a hot summer with a high amount of rain. We anticipate the pollen will be significant this year.”

Though timing and intensity of ragweed season vary depending on the region, it affects people across the country. August 15 is generally when it starts in the Upper Midwest and Northeast, while the South won't see higher ragweed counts until Labor Day, Fineman said.

“It really seems like every year it gets a little bit worse,” says Alan Reppert, a senior meteorologist with AccuWeather. “We've been seeing a lot of rain lately, and the ragweed season continues to be bad with plenty of moisture for the plants to grow. We see a lot more growing when we have higher temperatures, as well.”

Each ragweed-producing plant lives only one season, the Asthma and Allergy Foundation of America says, but that plant can produce up to 1 billion pollen grains.

Windy weather after sunrise generally helps to release the pollen, which then travels and fertilizes the seed so a new plant can grow.

In cities, the amount of pollen peaks between 10 a.m. and 3 p.m., depending on the weather.

Reppert said conditions typically are worse in late August toward September across the Mid-Atlantic and Midwest.

“It’s already starting off pretty strong,” Reppert said. “It’s been a high season so far, and we’re expecting that to continue.”

Reppert said the rainfall has been especially high in the eastern half of the nation, and that helps to bring moisture to all pollen-producing plants. Maps from the National Oceanic and Atmospheric Administration (NOAA) show that most of the country has recorded rainfall much above average this year, with some states such as Illinois, Ohio, and West Virginia having the highest levels ever recorded.

July brought some of the highest temperatures on record across the country, Reppert says. Much of the Southeast has recorded above-average temperatures, while Florida has the hottest weather ever recorded from January to July this year, NOAA maps show.

“From the Plains onto the East, we're expecting the warm conditions to continue, and temperatures will be slower to drop off,” Reppert says.

Ragweed allergy symptoms can vary widely -- from mild discomfort to sinus infections, Fineman says. Common symptoms are sneezing, a runny nose, congestion, headaches, irritated eyes, and an itchy throat. It can also affect energy levels, he says. There are 17 varieties of ragweed.

People who have allergies can ease the effects, he says. Doctors say the first step is to cut back on exposure by avoiding outdoor activity in the morning and early afternoon. And you should see your doctor for treatment early in the season. In some instances, you may need to see an allergist and have a skin test, so they know exactly what you are allergic to if symptoms are difficult to control.

The allergist can help with a management plan, Fineman says. This often includes nasal steroid sprays or other over-the-counter antihistamines. He says allergy shots are often an effective way of building a patient's tolerance to allergens.

Unfortunately, Fineman says, there are no signs that the intensity of ragweed season will let up anytime soon.

“The fact is that the climate seems to be warming now,” he says. “And that’s causing ragweed counts to be more potent.”

Show Sources

Alan Reppert, senior meteorologist, AccuWeather.

Stanley Fineman, MD, allergist; former president, American College of Allergy, Asthma and Immunology.

American College of Allergy, Asthma and Immunology.

Asthma and Allergy Foundation of America. Allergy Tracker.

National Weather Service.

National Oceanic and Atmospheric Administration.

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