Just when you thought it was safe to put away your tissues and handkerchiefs, you find yourself needing to bring them out again. Yes, February to April is the period in which spring allergies in Japan are at their peak. Hay fever in Japan (花粉症 kafunshō, “pollen disease”) is most commonly caused by Sugi pollen (known as Japanese cedar), hinoki (Japanese cypress) and butakusa (ragweed pollen), which are the main culprits throughout the archipelago except in Hokkaido where many suffer from shirakaba (birch) pollen.
When the average daily temperatures reach 10 degrees Celsius, the dispersal of pollen begins. Much like in the cherry blossom season, the pollen starts in the south and moves northward from west to east in Japan. The kafunshō season usually starts at the end of January and peaks in the second half of March. The amount of flowering and pollen production depends mainly on the weather during the previous summer. Hot, long summers result in higher pollen production the following spring.
The increase in kafunshō, especially the allergies caused by cedar pollen, has much to do with Japan’s post-World War II afforestation policy as demand for timber grew and the nation rebuilt itself.
Cedar was the tree of choice, especially in eastern Japan, because it grew rapidly and could easily be turned into wood. In western Japan, on the other hand, the cypress was popular, but this tree also came with its own allergen risk.
What happened over the years was that with cheaper wood imports, and a decline in the number of workers in forestry, many of the trees that should have been cut were left unattended, resulting in massive pollen pollution. Most of the nation’s cedar trees today are 50 years old or older, considering that at 30 they are at their peak of pollen production.
The aging trend of these trees has continued ever since, and although their forest area has hardly increased since 1980, pollen production has continued to increase. In addition to this, rapid urbanization in Japan led to greater coverage of soils and lawns by concrete and asphalt. Therefore, the pollen that sits on such hard surfaces can easily return to circulate from slight winds. As a result, today, approximately 25 million people (about 20% of the population) suffer from this disease in Japan.
On the other hand, it is common for foreigners with less than one year of stay in the archipelago to remain immune during the first pollination because their organism should be exposed to pollen for a few months in order to develop this sensitivity, since “sugi” and “hinoki” are trees peculiar to Japan.
The eyes, nose and throat are the areas usually affected. The main symptoms are constant sneezing, secretion and nasal obstruction, itchy eyes and headaches. Depending on the person, an itchy throat, cough, diarrhea and itching may occur on areas of exposed skin such as the face and arms.
The first symptoms of kafunshō may occur during winter and colder periods, making it easy to be mistaken for an influenza or common cold. In case of suspicion it is advisable to consult with a doctor. One of the basic measures in the treatment of allergic diseases is to discover the cause of the allergy (the allergen) and seek to avoid it. The specialist can identify the type of allergy and prescribe the correct medications.
If you are allergic to pollen, you can lessen your exposure to it by taking some simple precautions in your daily routine during that season.
• Wear a mask when you are out.
• Do not leave windows and exterior doors open for extended periods.
• After entering the house, brush or change the clothes you wore outside.
• When returning home after your day, avoid walking around your house before bathing, pollen could be stuck in your hair.
• Do not dry clothes and laundry outside.