On a hot summer’s day, one tends to drink cold drinks and eat cold foods to try cool their body down. But an old Korean proverb states that one should control fire with fire (yiyul-chiyul, 이열치열, 以熱治熱). In other words, instead of drinking cold drinks, it is better for your health if you eat hot soup to combat the heat. When the temperature becomes hot, the body redirects blood flow to the skin to cool itself, meaning there is less blood flow to the organs and causing the internal temperature to drop. Although cooling yourself is good, having a cold drink rapidly on a hot day can suddenly cause a large temperature difference between the surface and the organs, leading to digestive problems. In severe cases, it can cause abdominal pain and diarrhoea, with a vicious cycle where the heat is trapped on the surface and you feel even hotter. Ergo, having a hot food like samgyetang (a Korean chicken soup with many nutritious foods to revitalise your health in the summer) warms the organs and allows for better communication between the organs and the skin to effectively overcome the heat.
The philosophy of yiyul-chiyul can be extended beyond the scopes of medicine. Just as the proverb defeat savages with savages (yiyi-jeyi, 이이제이, 以夷制夷) says, one can control a certain force by using the same force on it. A great example is backfires. A forest fire tends to be too large in area to be extinguished with water. But if you deliberately start a fire just beyond its trajectory, it will burn everything as it moves towards the forest fire. Eventually the two fires will meet and without any fuel to consume, both will be extinguished.