Have a stuffy nose, need to sneeze and feel feverish? The pandemic might make you think that you've got COVID-19. Instead, there’s a chance you have succumbed to a growing seasonal health problem in Japan and elsewhere: fall allergies.
Unlike allergies from cedar and cypress pollen, which hit in the spring, fall allergies — caused by several grasses and weeds — are less recognized in Japan, though they seem to be afflicting a growing number of people and could be worsening due to climate change.
Here’s what you need to know about fall allergies:
What are the main sources of fall allergies in Japan?
While many think of pollen allergies as something that affects people in the spring, due to the pollination of cedar and cypress trees during the season, pollen can also wreak havoc at other times of the year, experts say. Unlike cedar and cypress pollen, which travel from tall trees, pollen is dispersed from grass and weeds close to the ground.
The ragweed pollen season starts in July and peaks in late September. Mugwort pollen also starts at the same time and peaks in September, while pollen from Japanese hop spreads from August through early November.
Experts say that some cedar that have problems maturing in the spring do so in the fall, spreading pollen in the process.
How common are these fall allergies?
In a nationwide survey of ear, nose and throat doctors and their families, 42.5% of the respondents had some form of pollen allergy in 2019, up from 29.8% in 2008 and 19.6% in 1998. In each of the three years when the survey was conducted, cedar was the leading cause of pollen allergy, affecting 38.8% of those surveyed in 2019, while 25.1% were found to have other kinds of pollen allergies, including from weed pollen.
Seiyo O, a professor of environmental engineering at Saitama University, said the protein structures of cedar and ragweed pollen are similar, pointing to the possibility that people who are allergic to cedar pollen will also develop allergic reactions to ragweed.
Unlike for cedar pollen, it is difficult to forecast the daily dispersal level of weed pollen, O said, because it flies only about several hundred meters, whereas cedar pollen travels several hundred kilometers. The volume of weed pollen people are exposed to varies greatly depending on the vegetation in their surrounding environment, although weeds grow anywhere from parks and river banks to the roadside.
During the pandemic, many people have adopted a habit of regular jogs or walks in their neighborhoods, often without masks, and without realizing the risk of being exposed to weed pollen, he said.
In the U.S., ragweed allergy affects an estimated 15.5% of the population, according to the U.S. Environmental Protection Agency.
The agency also says that climate change has worsened the problem: Warmer spring temperatures have caused some plants to start producing pollen earlier, and increased carbon dioxide concentrations have allowed ragweed and other plants to produce more pollen. As a result, the allergy season is now longer, and pollen counts are higher in many locations, according to the EPA.
In Japan, too, places such as Hokkaido that have long escaped the effects of cedar or ragweed pollen might be affected in the future, as warmer temperatures would expand their habitat, O said.
“It will be a nationwide problem, as weeds can grow anywhere,” he said.
The problem is exacerbated by the fact that pollen mixes with other pollutants in the air and fragments into smaller particles. O, who has long studied the link between pollen and air pollution, has shown that the surface membranes of pollen particles are damaged as the pollen comes into contact with pollutant chemicals in the air.
Once pollen particles break down, they can measure as little as 1.1 micrometers and can therefore be more easily ingested by people. These tiny particles accumulate in the respiratory tract or lungs and trigger symptoms such as coughing or even asthma, O said.
What are some of the other symptoms?
Typical symptoms of fall allergies are no different from ones caused by cedar and cypress pollen: sneezing, runny nose, congestion and itchy eyes.
Symptoms of pollen allergy and the omicron variant of the coronavirus are similar and hard to distinguish, experts say, but itchy eyes and nose tend to be more strongly pronounced among people with hay fever, while for such people a fever of 37.5 degrees or higher is rare, they say.
Some people also experience itchiness in their mouth and throat immediately after eating fresh fruit or vegetables. This is called oral allergy syndrome and is caused by allergy antibodies in your body mistaking certain proteins in fresh fruits or vegetables for pollen. For example, exposure to mugwort pollen is associated with an oral allergy for peaches, while ragweed pollen is known to make some people hypersensitive to melons and bananas.
How do you get diagnosed and get relief for fall pollen allergy?
Ear, nose and throat doctors can diagnose all pollen allergies. In addition to asking about your symptoms, your allergy history and the allergy susceptibility of your family members, doctors may take a sample of your nasal mucus and check whether it contains acidophilic leukocyte, a type of white blood cell whose level is known to spike in allergy patients. Doctors may also carry out a skin or blood test to see if your body has created anti-allergen antibodies.
Treatment options depend on how severe your symptoms are, but avoiding pollen exposure is the most important step in preventing and alleviating symptoms. In its 2022 pollen allergy guidelines, the Environment Ministry recommends the use of masks and eye glasses outdoors to keep exposure to pollen to a minimum. It also advises you to avoid wearing wool clothes when you go out, as pollen is known to stick to them particularly well.
Inside your home, opening windows to let fresh air in could draw in a massive volume of pollen, so the ministry recommends cleaning floors and washing curtains regularly.
People with severe symptoms can get a range of medicine prescribed, such as oral antihistamines and corticosteroid nasal sprays. The academic society of nasal allergy doctors in Japan recommends that people consult with doctors early on in the season, even when they intend to use over-the-counter medicine. Pregnant women are asked to avoid medicine as much as they can until they are 4½ months into their pregnancy.
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