Disposable body warmers, or kairo, are one of the Japanese inventions that really surprised the world.
Japanese disposable thermochemical heating pads are a great example of how innovation can make our lives easier and more comfortable in any environment. They have become not only a practical but also a valuable attribute of Japanese culture, which maintains the tradition of comfortable and warm rest, while maintaining health and good mood.
In 1978, Lotte Health Industry and Bionics jointly developed a disposable thermal heating pad called Hokalon. An interesting fact is that the inventor company Lotte is a confectionery manufacturer.
KAIRO’S USES
Due to their small size, kairos have opened up many possibilities. They really have a great potential to improve comfort and health. Here are a few interesting aspects of using Japanese disposable thermochemical hot water bottles.
Keeping warm outside. If you’re planning a long walk, hike, or trip outdoors, a kairo will help you stay warm and comfortable. This is especially useful in mountainous regions and cities, where cold weather can be an obstacle to good rest.
Maintaining health. Using kairos can be useful for maintaining health in cold weather. They help to avoid hypothermia and the likelihood of diseases associated with low temperatures.
Thermal heating pads can be helpful for people with muscle and joint pain. The heat helps to relax the muscles and relieve discomfort.
Kairos can be useful for workers who perform their duties outside even in cold weather. Improving work efficiency, such as electricians who have to work in extremely cold conditions or mountain rescuers. By keeping warm, you can increase your productivity and concentration at work.

A LITTLE INSIGHT INTO THE HISTORY OF THE MOBILE HEATING PAD CONCEPT
The use of the heaters dates back to the Edo period. Back then, these hot water bottles looked quite different from the ones we have today, as they consisted of specially heated stones that were wrapped in cloth and placed under the arm to warm you up. This practice was called onjaku.
Salt or a mixture of salt and ash was also used at this time. The salt or salt mixture was roasted and wrapped in a cloth to create a thermal heaters.
Later, in the Meiji era (1868-1912), heaters using ash appeared. In this case, a mixture of coal powder and ash was placed in a special metal container. This container was then covered with a cloth and used as a heating pad. Interestingly enough, these ash-based heating pads are still available today.
In the 1970s, disposable heaters were developed that utilized the heat generated during the iron oxidation reaction. These heaters called kairo became extremely popular due to their ease of use.
Specialty disposable heaters with stickers and labels were first produced in 1988. Since then, the market for such heaters has expanded significantly, introducing various variations, including mini heating pads, shoe warmers, and even pillow-shaped heating pads that have become indispensable wintertime helpers.
USING KAIRO IN CRITICAL CONDITIONS
In February 2024, due to the full-scale aggression against Ukraine, Japanese partners offered various Ukrainian organizations to receive kairos as humanitarian aid. Due to the loss of seaports, importing or importing products from Japan has become very difficult, so in critical conditions, in the absence of electricity, the use of kairos has proven to be very important – heaters do not weigh tens of kilograms, unlike, for example, a generator, and can be sent by anyone from Japan because of their light weight. Thanks to the efforts of the Association of Japanese-Ukrainian Cultural Exchange and its director, Mr. Ono Motohiro, this campaign began to become a national event with the beginning of winter in 2022. Those who wanted to help Ukrainians survive the war sent heaters directly to many organizations and volunteers.Thus, a joint humanitarian action “Warm Ukraine” was created, the network of recipients of which included well-known Ukrainian NGOs and charities.

The geography of the distribution of hot water bottles was impressive.