Blooming flowers and new growth on trees make spring a beautiful time of the year. But for many people, all of this new growth only brings suffering in the form of allergies. Some people claim that each year their allergies seem to get worse and worse.

Well, they are likely right.

Environmental experts and public health researchers are all saying the same thing: Climate change can make allergies more severe and allergy seasons longer.

A study published in the March 2019 journal Lancet Planetary Health found that pollen counts in the Earth’s northern hemisphere have been increasing -- along with a rise in temperatures.

The lead writer of that study is Dr. Lewis Ziska, a scientist at the United States Department of Agriculture (USDA). For the past 20 years, he has been studying the effects of climate change on allergens.

Allergies impact millions of people around the world. Experts at the Allergy and Asthma Foundation of America say allergies are one of the most “common chronic diseases.” A chronic disease is one that causes problems often or long-term.

On its website, the Academy claims that between 10 to 30 percent of the world’s population suffers from hay fever, a type of allergy. Many people experience allergic reactions to tree pollen, grass pollen, ragweed pollen and more.

But now, back to Ziska and his research. In this most recent study, he and his team studied 17 locations in North America and Europe as well as the following countries: Australia, Brazil, Chile, China, Egypt, India, Iran, Japan, Mexico, Saudi Arabia, South Africa and South Korea.

The researchers found that 12 of those 17 places showed “significant increases” in pollen levels. And 11 of the 17 showed a “significant increase” in the length of allergy seasons.

He and another USDA researcher, Frances Caulfield, looked at the effects that rising carbon dioxide levels were having on the production of ragweed pollen. Ragweed is a common allergen, especially during the fall.

The researchers grew ragweed in a controlled environment and increased the carbon dioxide levels in the air. They found that ragweed plants produced much more pollen when carbon dioxide levels increased. Increased carbon dioxide in the air may also lead to ragweed pollen that is stronger, or more allergenic.

In a report published in 2010 by the U.S. National Wildlife Federation and the Asthma and Allergy Foundation of America experts give a detailed explanation on how climate change is affecting allergen-producing plants.

For one thing, warmer temperatures are making the growing season for some allergen producers longer. And, the report says that some plant species may react better to increased levels of carbon dioxide (CO2) than others. For example, as the climate warms, the areas for major allergen-producing trees such as oak are getting larger.

Ziska warns that not all places are being affected by rising levels of CO2 in the same way.

“A city is different than the surrounding countryside. Cities are heat sinks. Trees, for example, in the spring...they tend to flower earlier in the cities because it’s warmer. Cities heat up faster.”

Exercise 1


Read the following vocabulary with your teacher.

bloom n. the flowering state

pollen n. very fine, yellow dust that is produced by a plant and is carried to other plants by wind or by insects

hay fever n. allergy usually caused by pollen

significant adj. large enough to be noticed

heat sink n. something that absorbs (or dissipates) especially unwanted heat


Exercise 2


Answer these questions about the article.

1. How does climate change affect allergies?

2. How many people around the world suffer from hay fever?

3. According to Ziska's research, how many places showed “significant increases” in pollen levels?

4. Why do trees flower earlier in cities compared to the countryside?


Exercise 3

Make a sentence.

Make sentences using these words.

bloom, pollen, hay fever, significant


Exercise 4


Have a discussion on following questions.

1. Are you surprised by the findings of Ziska's research?

2. Do you suffer from any allergies?

3. Are allergies common in your country?

4. How does climate change affect your life?



This lesson is based on a news article originally published by VOA.