Hot water can dilate skin blood vessels, while cold water can contract blood vessels. Alternating hot and cold water is like letting blood vessels do gymnastics. If we can persist for a long time, the human body can better adapt to the cold and hot changes of the external temperature. It can not only prevent allergic rhinitis, but also prevent colds and chilblains, improve breathing and increase vital capacity.

Cold water has an exciting effect on the brain and nerves, which makes the mind clear, while hot water can relieve fatigue. After a hot and cold bath, I feel very relaxed all over.

Extended data:

Precautions:

1, full or empty stomach is not suitable for bathing: after each meal, the human body should transfer some blood from the whole body to the stomach to help digestion. Taking a bath immediately after a meal, on the one hand, will aggravate heart ischemia, even angina pectoris or sudden death, on the other hand, due to the reduction of blood flow in the digestive tract, it will affect the digestion and absorption of food and induce symptoms such as nausea, vomiting and epigastric pain.

2. Keep warm before and after bathing. Keep warm during and after bathing, especially for the frail elderly. Before taking a bath, the temperature in the bathroom should not be cold after undressing. Dry your body with a dry towel after bathing and put on clothes as soon as possible.

3, soap should not be too much, just take a shower and wipe the soap once, too much will irritate the skin and cause itching. People with dry skin, the elderly and children are suitable to use fat soap, and do not use alkaline soap or hot water to scald, so as not to wash off sebum, make the skin drier and even wrinkle. Some people have greasy skin and can use neutral or alkaline soap.

Baidu encyclopedia-bathing

Baidu encyclopedia-hot and cold bath