First, it may be that you have eaten something that causes internal heat recently, such as hot food, snacks or other things that are not easy to digest, and at the same time you did not drink enough water to reduce the internal heat.

Second, if you are under great pressure or have many worries, you will easily become upset and have a bad temper, which will cause excessive liver-fire and lung-fire.

Third, the work and rest are irregular and the body circulation is blocked.

Fourth, sitting for a long time without exercising will lead to blocked blood vessels.

Fifth, environmental reasons, such as acclimatization, dryness and water shortage during autumn and winter, etc.