Foot warmers are generally sold in pharmacies. As the name implies, warm baby foot patch is another small-sized product of warm patch. Foot stickers, also called mini stickers and small stickers, are used in places where big warm stickers are inconvenient. Like the soles of your feet, or your joints. The reaction principle is also to convert chemical energy into heat energy by redox reaction. In order to make the temperature last longer, the product uses the mineral material vermiculite to keep warm, and more importantly, let the oxygen enter slowly. The charging bag is made of special materials and consists of a raw material layer, a gelatin layer, a breathable film and a non-woven bag. Non-woven fabrics should be attached with microporous breathable films. In addition, there must be a conventional airtight outer bag-commonly known as plastic bag. When in use, the outer bag is torn, so that the inner bag (non-woven bag) is exposed to the air, and oxygen in the air enters the interior through the breathable film. The heating time and temperature are controlled by the oxygen permeability of gas permeable membrane.