Even in winter you can see girls with short clothes in Japan. If you ask how they endure the cold, most of them will tell you that they wear “Kairo”. Kairo are pocket warmers that function as a portable heat source under the jacket. The most widely used brand is called “Hokkairo” in reference to the Northern island of Hokkaido.
These small and airtight paper bags include iron powder, activated carbon, water, cooking salt and a mineral called vermiculite. After opening the packaging, the iron powder combines with the oxygen in the air and oxidizes. In combination with the other ingredients, this reaction then generates a fair amount of heat.
Haru Cairo “貼 る カ イ ロ” is the most practical. To open the pack, simply tear at the specified area and remove the adhesive protective strip from the white paper bag. It then takes about 5 minutes before the Kairo has reached temperature. Never cut the bag to open it as this will damage the Kairo and is potentially dangerous.
We recommend you place the Kairo on the outside of your clothes in the waist or back area. It sticks rather tightly, so be careful with sensitive materials like silk or wool and do not put it on your skin directly. Here are a few more general facts about Kairo.
Average temperature (平均気温): 60 to 70 °C
Duration: 8h to 12h
Hokkairo are odorless and have an expiration date.
They are sold at supermarkets, drug stores and Konbinis for under 100 yen.
Keep yourself warm with Kairo during the winter season!