Some gray hair is caused by sun exposure? African friend: Are you polite...

“Some white hair is caused by sun exposure”

Recently, an article on the Internet stated that the scalp can be damaged by ultraviolet rays, so sun exposure may be one of the causes of more gray hair.

Rumor Analysis

In fact, this statement is not very rigorous.

It's very simple. If you often bask in the sun, your hair will turn white. So do African friends (or friends in the south) who live near the equator have white hair? Obviously not.

As the Buddhists say: There are three thousand strands of trouble, and each strand is better than the last strand. Nowadays, hair really brings troubles to many people. One trouble is hair loss, which we have talked about many times. Another trouble is gray hair. There are many different opinions about the causes of gray hair, and some even think that sun exposure is an accomplice. Is this really the case? What is the reason for gray hair? Today, let's talk about it.

Can hair be tanned?

Let me first state the conclusion: this risk is small and there is no need to worry too much. There is a saying on the Internet that if you frequently bask in the sun, the "photobleaching" reaction will degrade the pigment of your hair and turn your hair "white".

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In fact, this statement is too arbitrary. It is very simple. If frequent exposure to the sun will cause gray hair, then do African friends (or friends in the south) who are close to the equator have gray hair? Obviously not.

Let's talk about the data. Some scholars have found that, on average, Caucasians' hair starts to turn gray around the age of 35, Asians' hair starts to turn gray around the age of 30 or 40, and Africans' hair turns gray the latest, around the age of 45. Even the Bantu people in Africa rarely have gray hair before the age of 40 to 50. From this, we can feel that the effect of ultraviolet rays does not seem to be as great as rumored.

The real reasons for white hair may be these

Next, let's talk about the causes and triggers of gray hair. In fact, there are too many causes of gray hair, and the relationship with ultraviolet rays is not particularly clear. Although it can be seen in the medical database that ultraviolet rays have a negative impact on the hair of mice, this is not convincing enough because it is based on animal experiments under ideal conditions, and the conclusions cannot be simply copied to humans. What's more, there is no human research on the relationship between sun exposure and gray hair.

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Gray hair is actually closely related to age, genes, race, hair color, etc., as can be seen from the statistics mentioned above. This may be related to external factors, but the relationship is relatively weak and not very universal. Sometimes, gray hair may be related to ultraviolet rays, stress, smoking, medication, malnutrition, immune diseases, etc. But we don't need to exaggerate these risks to avoid causing unnecessary anxiety and panic. As scholars have admitted, there is actually no answer to whether external factors (such as ultraviolet rays) are at work in the process of hair graying. If you want to summarize the real cause of gray hair in one sentence, you can say this - gray hair is mainly determined by genetic factors, but sometimes various environmental factors will be involved.

How to prevent gray hair?

This question may sound familiar, and it reminds people of the question in Journey to the West, "How can one achieve immortality?" These two questions have one thing in common, which is that they are both a bit embarrassing. To be honest, graying hair may not be preventable, because there are many fundamental factors that cannot be changed, let alone reversed, such as age and race. Therefore, we need to adjust our psychological expectations and not have too high expectations for any preventive measures. This does not mean that there is nothing we can do. Some measures may have some potential benefits. For example:

①Ensuring a balanced diet may help slow down the formation of gray hair. If there are deficiencies in certain nutrients, such as calcium, ferritin, vitamin B12, etc., you should pay attention to correcting them because they are related to premature gray hair.

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② Lifestyle factors such as smoking and mental stress are somewhat related to gray hair. Therefore, improving your lifestyle and trying to live a healthy life, such as reducing stress and quitting smoking, may slow down the formation of gray hair.

③Although there are few studies directly on the relationship between ultraviolet rays and gray hair, considering the potential negative impact of ultraviolet rays on skin and hair health, paying attention to sun protection on a daily basis may also play a certain preventive effect.

④ Some topical products also seem to have the prospect of preventing gray hair. For example, Koreans once recruited people for research and found that Pueraria extract has a certain preventive effect. Its preventive effect comes from antioxidant activity and promoting the expression of melanocytes. However, this study was funded by a company and is not particularly credible, but fortunately there is hope.

My hair has already turned white, what else can I do to cure it?

Although modern medicine is very developed, it is still a bottleneck to effectively treat gray hair. We know that most people's gray hair is actually just a cosmetic problem. As they get older, gray hair will slowly grow out. If you don't mind this kind of beauty, you can live in peace with them, which is at least better than hair loss. If you mind, you can still find a way. If there are a lot of white hair, you can directly choose hair dye, which has an immediate effect. But there are two disadvantages. One is that the newly grown hair is still white, and the speed is about 1.3cm white every month. The other is that there is a small probability of irritation and allergy to hair dye, which manifests as itching and rashes on the skin at the contact site. If there are few white hairs, you can cut them off at the root of the white hair with clean scissors or nail clippers. This is safe and risk-free, but it will be repeated every few months. I believe that some people choose to pull them out directly. Objectively speaking, it is not impossible to do so. However, from a medical point of view, it is not recommended. Firstly, this will damage the hair follicles, and it is possible that every time a hair is pulled out, there will be one less hair. Another is that there is a risk of local infection, and bacteria will take the opportunity to enter the wound and cause folliculitis, which manifests as small red particles or white pustules.

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So, in summary, sun exposure usually does not make hair turn gray, and the main cause of gray hair is genetic factors. As for external factors, such as ultraviolet rays, stress, smoking, malnutrition, etc., they may have some influence, but the overall relationship is not that great. The method to prevent gray hair is not very accurate, but it may be helpful to maintain a balanced diet, improve lifestyle, pay attention to sun protection and use certain topical products, but don't expect too much. For hair that has turned gray, you can choose to dye it or cut it off, but it is not recommended to pull it out to avoid damaging the hair follicles and infection.

Looking in the mirror of rumors

Many rumors that come from life are actually "generalizations". At first glance, they seem to make sense, but in fact, there is no substantial research to support them. When we encounter such rumors, it is best to take some examples that match them and ask whether they are true. If they are not true, the rumors will be self-defeating.

Author | Tang Jiaoqing, attending physician of dermatology, doctor of medicine, popular science author

Review | Feng Jun, deputy chief physician of the Dermatology Department of Sinopharm Tongmei General Hospital