Why are people's lips red?

Because the face is an important part of the human body, people's five senses all grow on the face. There are a lot of blood vessels in these parts, and blood flows in them. Lips are one of the most sensitive and soft parts of the face. There are many capillaries in the mouth, and the lips belong to mucosal organs. Its skin is particularly thin and transparent, and bright red blood can penetrate under the skin, making the lips appear red. So the red color of lips is actually the color of blood.

Extended data:

Licking your lips is a bad habit that can easily lead to chapped lips. When the lips are dry, many people will lick them subconsciously. But licking your lips will not only make your lips moist, but also aggravate the degree of chapping and may even cause cheilitis.

In fact, the stratum corneum of human lips is very fragile, only one-third of the facial skin, and cannot automatically secrete water and oil, so it is extremely sensitive and easily affected by the surrounding environment and becomes dry. Once the saliva on the tongue touches the mouth, it will also take away the original moisture on the lips during evaporation. At the same time, digestive enzymes in saliva can also make lips dry, wrinkle and even cause cheilitis.

Popular Science China —— Lips: A Health Alarm.