Washing Hair in the Evening Does Harm to Your Health
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As we know, the rhythm of modern life is so intense. People are busy with their work, activities and entertainment during the day. Therefore they like washing hair in the evening when they are free.
Of course, it is OK if you have enough time for the hair drying out when you wash hair in the evening. But sometimes you are too busy to wash hair before 10 pm, and you feel so tired after washing that you always go straight to bed and sleep before the hair is totally dry. To do so, the elders will say that will cause headache later. In fact, their words are somewhat reasonable through modern scientific research.
We must know that the human body always produce heat continuously in the metabolism process to maintain the body temperature. And the heat would be transferred to surface layer of organism through blood circulation and emanated to the outside with ways of radiation, conduction, convection as well as evaporation.
For those with strong body resistance and normal regulating function, the two processes of heating and cooling are in balance, that is to say heat will increase when the body temperature declines, which make the body temperature remain at around 37 C. But for people who have weak body resistance and poor regulating function of body temperature, they are easy to get cold by whole or local exposure to cold.
After we wash hair with warm water, the capillaries of the scalp will dilate due to warm effect and the heat of the body radiating around will increase. Meanwhile, the wet hair will cause a lot of water to evaporate, which take away much heat. Generally speaking, 500 calories will be taken away when one gram of water evaporates.
As the heat loss increases and the body gets cold, the capillaries of the upper respiratory tract shrink reflectively, partial blood flow volume reduces and the resistance of the upper respiratory tract decreases, which lead to that existed virus or bacteria get a chance to step in, grow and reproduce. It will result in the respiratory tract infections, which make people have flu symptoms such as runny nose, stuffy nose, headache or fever.
So generally speaking, you should avoid washing hair before going to bed. Even if you had to do that, you should towel your hair dry. In this way you will not catch cold.