“Asemo” or heat rash, is a common condition seen in most babies, and also appears in Haiku, such as this piece by Takahama Kyoshi:
◆ Naku koe no ooinaru kana asemo no ko (Baby’s loud crying, heat rash)

Since the Edo Period, people seemed to try any powder around home on the heat rash, including rice, wheat, and soba flours.

An Edo Period o-rai-mono (equivalent of a modern day textbook) titled “Joyou Kunmou Zui” (Illustrated Textbook for Women) from 1687, about the knowledge a woman should have, stated “a good way for treating heat rash is to roast hamaguri clam, mix its powder in wheat flour, wrap in cloth, and shake over (the rash site).”

Another book, a typical child care text in the Edo Period titled “Shoni Hitsuyou Yoikuso” (Essential herbs to rear a child) from 1703, stated, “… applying powder of oyster, arrowroot flour, or tenka-fun is a good way to prevent heat rash in summer. In any case make sure that the powder applied is fine …”

As seen in those examples, during the Edo Period a widely practiced wisdom was to apply rice flour, oyster powder, arrowroot flour, tenka-fun, or finely ground tea on an infant’s skin after bathing. “Shoni Hitsuyou Yoikuso” gave further commentaries, such as rice flour is not good as it could be pest infested; powder of oyster, arrowroot flour, or tenka-fun is a better option.” “If the skin is raw under the chin, on the groin, or in the armpit, applying tenka-fun, etc., after a bath is a good way to treat it, etc.

Judging from child care textbooks such as “Ikueiso” (Child care herbalist) from 1877, applying arrowroot flour, finely ground tea, wheat flour, buckwheat flour, or such powder seemed to be widely practiced heat rash treatment in the Meiji Period. Descriptions of flowers of zinc (zinc oxide) application first appeared in the mid-Meiji years. By the late Meiji Period, flowers of zinc - starch preparation become widely used.