Hay fever (花粉症)

Amber Chang, International Affairs Division

Hay fever, known as kafunshō in Japanese, is an allergic reaction caused by airborne pollen of specific seasonal plants.

Kafunshō is characterized by nose (runny or stuffy nose, continual sneezing) and eye (itchy or watering eyes) symptoms. However, the effect can differ greatly from person to person, and some may suffer from symptoms like throat and skin irritability, or even diarrhea, headache, and fever in more severe cases.

Grasses (Family Poaceae/イネ科) in European countries, ragweed (ambrosia/ブタクサ) in the United States, and Japanese cedar (杉) in Japan are said to be the three hay fever sources of the world. In Japan, the Japanese cedar, called sugi (杉) in Japanese, and hinoki (檜) are considered to be the two most important allergenic tree pollens, and an estimated 20% of the population experience hay fever from these pollens according to statistics.

Among sugi and hinoki, a majority of hay fever sufferers are sensitive to sugi pollen grains in particular. One of the reasons is said to be the presence of a huge area of cedar forest which makes up some 12% of the nation's total land area. Generally, hay fever is prevalent from mid-February to mid-May in Japan, but there are also people who suffer from hay fever throughout the year.

In Japan alone there are over 60 sources of allergenic pollen. According to the data from the Health Services Disease Control Division of the Department of Health and Social Services, Ibaraki Prefecture, various types of pollens are scattered in the air all through the year:

  • February–April: sugi pollens
  • April–May: hinoki pollens
  • June–August: grass pollens
  • August–October: ragweed pollens

So, why do some people show obvious reactions and some do not? And why do some people with previous experiences of hay fever in their home counties appear unaffected during the hay fever season in Japan? As it was mentioned before, hay fever is an allergic reaction caused by airborne pollen, but the predisposition and degree of this allergy is related to both heredity and environmental exposure. As sugi and hinoki are unique to Japan, the allergic reaction for first-time visitors won't likely to show until after a certain length of exposure (i.e. inhalation) to the pollen. Therefore, even if a person has previous hay fever symptoms in his/her home country, it is common for no symptoms to occur in one's first pollen season in Japan, and likewise when Japanese go abroad.

So, lucky you if you are only visiting Japan temporarily! But if you are intending to stay for some time still, it may be worthwhile to keep some prevention methods in mind, because . . . you may start to experience allergic symptoms from the next spring onward!

Avoiding exposure to pollen in the hay fever season is considered the best way to reduce allergic symptoms.

Suggested prevention methods:

  • Wear face masks to filter out pollen. Masks can effectively filter out 1/3 to 1/6 of the inhaled pollen amount.
  • Glasses and sunglasses are good to prevent 1/2 to 1/3 of pollen from entering the eyes.
  • Regular hand- and face-washing can reduce pollen inhalation through the nose, and gargling can remove already-inhaled pollen from the throat.
  • Do not dry clothes outdoors.
  • Remain indoors when the pollen levels are high, and keep windows closed if possible.
  • Wear a hat to reduce pollen contact with the hair.
  • Avoid wearing woolen clothes or coats during this period as pollen can easily stick to them. Wearing clothes with smooth texture, like cotton or polyester, can hopefully reduce the amount of pollen sticking to them, therefore reducing the likelihood of pollen inhalation.
  • Maintain a healthy lifestyle (enhance your immunity) and avoid unnecessary exposure to environmental irritants like cigarettes, insect sprays, air pollution, etc.

Hope this is something useful to everyone, and good luck!