There are many cedar trees in Japan.
As a national policy, many Japanese cedars were planted in Japan after the WW2.
The policy was sufficiently helpful to supply the material of the product, but it produced byproducts.
It is hay fever.
Currently, many Japanese people are suffering from hay fever.
It is surprising that many Japanese are masking if you come to Japan for this season of cherry blossoms bloom.
Hay fever is said to occur by excessive work of the body 's defense instinct.
In other words, a person who comes to hay fever can be said to be a healthy testimony that defense instinct is working.
SAYONARA.