Can science explain the legend of “turning hair white overnight”?

Many people have seen the scene of "turning hair white overnight" in movies and TV dramas, and they believe it without a doubt.

In fact, the saying " turning hair white overnight " has been circulating in China since ancient times, and there are many folk stories about it, including the most famous story of "Wu Zixu".

Wu Zixu was a famous military strategist during the Spring and Autumn Period and the Warring States Period. His father was Wu She, a doctor of the State of Chu. At that time, King Ping of Chu believed in slander and wanted to kill Wu She, and ordered his son to be recalled. Wu Zixu hurriedly fled when he heard the news. So King Ping of Chu asked his subordinates to take the portrait and arrest him everywhere. Wu Zixu tried every means to avoid being tracked down. When he was about to defect to the State of Wu, he found that it was heavily guarded when he passed Zhaoguan. Moreover, Zhaoguan was between two mountains, facing the river, and the terrain was dangerous. Under tremendous pressure, Wu Zixu's hair turned white overnight, so he took the opportunity to change his clothes and passed Zhaoguan without being recognized.

These stories have been exaggerated to a certain extent since they were passed down to the modern times, but they are still deeply rooted in people's hearts, and the saying "turning hair white overnight" has also begun to spread.

But does this phenomenon really exist and what is its scientific basis?

The structure of hair

From a structural point of view, hair mainly consists of two parts: hair root and hair shaft . The hair shaft is exposed outside the scalp, the part we can usually see, and it is also the main object of daily care; the hair root is located inside the scalp, and its main function is biosynthesis and directional growth.

Generally speaking, the cross-section of the hair shaft can be divided into three layers : cuticle , cortex , and medulla .

The cuticle is the outermost layer of the hair shaft and is composed of a roof-tile-like structure. It is a cross-linked protein-lipid structure that provides a certain barrier effect to prevent hair damage.

The cortex is the middle layer and the main structure of the hair. It is composed of keratin. The matrix of the cortical cells contains pigment particles , and the amount of pigment particles determines the color of the hair .

The medulla layer is the center of the hair shaft, surrounded by the cuticle and cortex. It is a discontinuous structure that determines the softness, hardness and thickness of the hair.

There is no scientific basis for " white hair overnight "

The color of hair, that is, the content of pigment granules, is determined by genes and the acquired environment. Asians have black or brown hair because it is rich in melanin, while people with yellowish or reddish hair tend to have another type of brown melanin. White hair has no or very few melanin granules.

Hair color is also related to metal elements . For example, black hair contains more iron and copper, while nickel can cause gray hair.

At the same time, hair color is also related to mental state and nutritional level . High work and life pressure can easily lead to mental tension and depression. Long-term stress and disordered work and rest can cause endocrine imbalance and premature graying of hair. Certain diseases such as progeria and albinism can also change hair color, but these are all caused by a period of time and gradually lead to graying of hair .

At present, no research has shown that hair can turn white quickly in a very short period of time. In other words, it is impossible for black hair to turn white overnight due to the body's own physiological regulation without chemical bleaching and dyeing .

Why does the feeling of " white hair overnight " occur?

The so-called hair turning white overnight is not really the hair turning from black to white, but the original black hair is mixed with white or gray hair. Due to some diseases or factors, the black hair that is in the growth period begins to fall off in a short period of time, and the proportion of the remaining white or gray hair increases. This obvious contrast makes people feel like "the hair turns white overnight."

Some scientists believe that turning hair white overnight may be caused by a physical and mental illness - alopecia areata. Ancient Chinese medical books call alopecia areata "oily wind" and "ghost hair loss". This is a rare autoimmune disease that is common in young and middle-aged people. Its cause is complex and is related to psychological factors. People with this disease will lose a lot of hair under the influence of huge psychological and emotional changes, and the amount of black hair that falls off is significantly more than white hair, creating the illusion of "turning hair white overnight".

Can gray hair turn black again ?

Gray hair is not irreversible. If the melanin abnormality is caused by certain acquired diseases, by removing the obstacle or pathogenic factors, the hair follicles can synthesize melanin again and the new hair will turn black.

In daily life, keep a good mood, pay attention to a balanced diet, eat more dietary fiber, fresh vegetables, fruits, and foods containing iron and copper, which can promote melanin synthesis and make hair darker.

In addition, you can also perform scalp massage frequently, which can accelerate local blood and cytokine circulation, increase nutrition of hair follicles, improve pigment cell function, enhance cell activity, accelerate division, and increase melanin secretion.

Of course, you should also pay attention to actively taking care of your hair , wash your hair at an appropriate frequency (2-3 days/time), pay attention to the stimulation of chemical products, try not to perm or dye your hair, and keep your hair in its natural state, which is the healthiest !

Now you know! The " white hair overnight " in movies, TV shows and allusions is just an exaggerated expression to describe worry and melancholy, and has no scientific basis . However, the nervous and endocrine dysfunction caused by negative emotions such as extreme tension and sadness can cause white hair in a short period of time by inhibiting the synthesis of melanin, so you must learn to adjust your state and relieve stress in your daily life!

Review expert: Zhang Yuhong, deputy chief physician of the Department of Dermatology, Zhengzhou Central Hospital Affiliated to Zhengzhou University