There seem to be all sorts of old superstitions and urban legends floating around, such as “eating wakame seaweed makes your hair grow” and “pulling out gray hairs causes more to grow.”

Here, we’ll debunk some common myths about hair and share the facts, along with tips for proper hair care.

Myths and Facts About Hair

Thinning hair runs in families → True

Human genes consist of X and Y chromosomes; males have an XY genotype, while females have an XX genotype. Since the gene for AGA (androgenetic alopecia) is located on the X chromosome (AR gene), if an X chromosome carrying the AGA gene is inherited, the likelihood of developing thinning hair increases. Because an XY genotype is required for male development, a boy must inherit the Y chromosome from his father.

Therefore, even if the father’s X chromosome carries the AGA gene, it will not be passed on to his sons. Only the mother’s X chromosome is inherited. During a consultation at an AGA specialty clinic, you will be asked, “Are there any men on your mother’s side of the family with thinning hair?” This is because the AGA gene is inherited from the mother’s side.

Therefore, even if your father does not have thinning hair, if your maternal grandfather does, there is a significant chance you will develop thinning hair. This is what is commonly referred to as “skipped-generation inheritance.” However, genetic factors are said to account for about 70% of the cause, so it is not a 100% certainty that you will develop thinning hair.

People with gray hair don’t go bald → False

Many people seem to believe that those with gray hair do not experience hair thinning, but this is completely false. It also appears that many people believe hair falls out and thins with age, or that it remains thick even after turning gray—essentially, that there are two distinct types.

The pattern where hair falls out and thins (AGA) occurs when male hormones convert into DHT (the hair-loss hormone), which triggers hair loss. Therefore, even in people with gray hair, male hormones are still present, and in fact, many people do experience hair thinning.

Gray hair is evidence that the melanin pigment in the hair has diminished due to the aging process. However, research has not yet proven whether the hair follicle cells that produce gray hair and those that produce black hair differ in their susceptibility to DHT (the hair loss hormone).

Stress causes hair loss → False

Many people seem to believe that leading a stressful life causes noticeable hair thinning, but this is completely untrue. The cause of AGA is the conversion of male hormones into DHT (a hormone that promotes hair loss); stress does not increase the amount of DHT or intensify its effects.

Even in the case of alopecia areata, which is said to be closely linked to stress, it cannot be definitively stated that stress alone causes baldness. It is believed that stress is not the direct cause, but rather that people who are genetically predisposed to alopecia areata use stress as a trigger to develop the condition.

Women don’t get thinning hair → False

Do you believe that women don’t experience hair thinning? This is a myth; women do experience hair thinning, and while it may not be as severe as in men, there are many women who struggle with it. Incidentally, it is said that approximately 50% of female hair loss cases are FAGA (Female Androgenetic Alopecia).

In Western countries, this is attributed to abnormal levels of male hormones in the blood caused by the influence of male hormones, but there are no similar reports in Japan. AGA is not exclusive to men; the term simply refers to androgenetic alopecia. Since male hormones are present in women’s bodies as well, women are indeed susceptible to FAGA.

However, the most significant difference between female and male AGA is that the concentration of these hormones in women is about one-tenth that of men. Consequently, the production of DHT (the hormone that causes hair loss) is lower, resulting in less severe hair loss. This makes female FAGA much easier to treat compared to male AGA.

Using cheap shampoo causes hair loss → False

People often say that using cheap shampoo is bad for your hair and scalp and can lead to hair loss, but this is also a myth. The cells responsible for hair growth are the hair matrix cells, which surround the hair papilla located several millimeters deep within the scalp, beyond the hair follicles.

No matter how vigorously you scrub with shampoo, while it may clean the scalp, the shampoo’s ingredients cannot reach the hair matrix cells located deep within the hair follicles. Therefore, since it does not affect the hair matrix cells responsible for hair growth, it does not lead to hair thinning.

 

However, the hair on the outer layer of the scalp can become damaged by using poor-quality shampoo, causing it to become thinner or frizzy. Brushing too vigorously can strip away the cuticles on the surface of the hair, causing damage. Even so, while the tips of the hair may be damaged, new hair grows from the hair follicles and pushes the old hair upward, so your hair will not become thin.

Washing your hair too often causes hair loss → False

It’s a common myth that washing your hair too often causes hair loss, but this is also untrue.

AGA is a form of hair loss related to male hormones, so it’s an internal issue. Since hair grows on the surface of the scalp, it has absolutely nothing to do with AGA. The hair matrix cells that produce hair are located several millimeters deep within the scalp, beyond the hair follicles, so shampoo ingredients cannot reach them and do not affect these cells.

However, washing your hair too often can damage it. Scrubbing your scalp with your fingernails can injure the scalp, and dandruff develops as the cells repair the damage. The basic rule is to wash your scalp gently using the pads of your fingers. Conversely, washing your hair very infrequently has no connection to hair thinning.

It is said that even in the distant past, when people washed their hair only once a month, the rate of hair thinning was about 30%, which is the same as it is today.

Wearing hats and letting your scalp get sweaty causes hair loss → False

Have you ever heard that wearing hats or helmets on a daily basis can lead to hair loss?

No, this is also a complete myth. About 90% of male hair loss is caused by androgenetic alopecia (AGA), which is triggered by male hormones in the body. In AGA, male hormones are converted into DHT, a hormone that promotes hair loss. This hormone acts on the hair matrix cells deep within the hair follicles, causing hair loss.

Therefore, this is caused by internal processes within the body. In contrast, a “sweaty scalp” is a condition that occurs on the surface of the scalp, so it has absolutely nothing to do with hair loss.

Exposure to direct sunlight (UV rays) causes hair loss → False

It’s often said, especially among young people who enjoy leisure activities and sports, that exposure to direct sunlight and excessive UV rays can cause hair loss. But this is completely false.

Melanin, the pigment responsible for hair color, is highly resistant to UV rays, so even if you get a little sun, it won’t cause hair loss. Since hair loss means that hair stops growing, the cause of hair loss due to AGA is an internal scalp issue related to male hormones.

While direct sunlight can damage the hair itself, it causes no damage to the hair-producing cells located within the scalp.

“Thinning hair is caused by scalp oil” → False

It might seem like having an oily scalp makes your pores clog and leads to hair loss, but since scalp oil doesn’t actually cause thinning hair, this is completely false.

This misconception stems from the misleading information promoted by hair growth salons and hair growth shampoo commercials. Advertisements often claim that “scalp oil clogs pores, preventing the skin from breathing, which leads to hair loss.” Hair growth salons sell their services by promising “thorough cleansing,” while hair growth shampoos claim they “thoroughly cleanse the pores.”

While this may seem plausible at first glance, the theory that scalp oil causes hair loss was proposed in the 19th century and has since been completely debunked. The cause of hair loss due to AGA is a mechanism in which male hormones are converted into DHT, a hormone that promotes hair loss.

Scalp oil, which is an external issue, has absolutely nothing to do with this mechanism. No matter how clean you keep your scalp or how completely you remove all oil, it is impossible for weakened hair to grow thick and long again.

Athletes and sports players are prone to hair loss → It’s hard to say

Don’t you find it interesting that many athletes and sports stars have well-developed muscles, yet many of them also experience hair loss? Currently, scientific opinions on this matter seem to be divided.

It is believed that having more developed muscles than the average person indicates higher levels of male hormones in the body, which have a stronger effect.

Since the cause of hair loss due to AGA is the conversion of male hormones into hair-loss hormones, it is thought that the greater the quantity and potency of these hormones, the greater the impact of the hair-loss hormones. However, this is still only a hypothesis.

People with thick body hair are prone to hair loss → It’s hard to say either way

It is often said that “the thicker a person’s body hair—such as on the legs or chest—the more likely they are to experience hair loss” or that “the thicker a person’s beard, the more likely they are to experience hair loss,” but it seems the evidence is inconclusive.

According to scientific research, the cause of AGA is male hormones. When male hormones are converted into DHT (a hormone that causes hair loss), hair loss is accelerated. Since male hormones are responsible for developing masculine physical characteristics, people with thick body hair and beards are thought to have higher levels of male hormone secretion. Consequently, the production of DHT, the hormone that causes hair loss, increases, raising the likelihood of hair loss.

Myths About Hair Growth Products

I’ve compiled a list of five common myths about hair growth products that are often seen online these days.

① Using hair growth products will make your hair grow

You might be surprised to learn that hair growth products do not actually promote new hair growth. Hair growth products are approved for “promoting hair growth, nourishing existing hair, and preventing hair loss”—meaning they help keep your current hair healthy. Claims like “using this will make hair grow” or “it will cure thinning hair” would be considered false advertising.

However, by improving the scalp environment and promoting hair growth, these products may ultimately help address thinning hair.

While we can’t say that “using a hair growth product will make hair grow,” you can expect it to help create an environment conducive to hair growth.

② Hair loss treatments can actually cause hair thinning

Generally speaking, using hair growth products will not cause hair thinning. These products are designed to improve the scalp environment and promote hair growth; as they are quasi-drugs formulated with safety in mind, they do not cause hair loss.

Since quasi-drugs are not classified as medications, they have no side effects, meaning they do not cause hair thinning or hair loss. However, if a hair growth product does not agree with your body and causes scalp inflammation or other issues, this could ultimately lead to further hair thinning. Additionally, a phenomenon known as “initial shedding” may occur shortly after you start using a hair growth product, causing an increase in hair loss.

However, this happens because the scalp environment is improving, and new hair is pushing out old hair. You should view this as a sign that hair is growing, so there is no need to be pessimistic.

③ Seaweed ingredients promote hair growth

You’ve probably heard the saying, “Eating seaweed like wakame makes your hair grow,” haven’t you?

However, there is no scientific basis for this claim. That said, it’s not as though the nutrients in seaweed are completely useless. For example, wakame is rich in minerals—such as iodine—that support metabolism and are essential for hair growth. In that sense, it can be described as a food containing nutrients that are beneficial for hair growth.

④ Hair growth products are effective for gray hair

Many people seem to think, “If it’s an ingredient in a hair growth treatment, it must be good for gray hair too,” but hair growth treatments are primarily designed to promote healthy hair and improve the scalp environment. In contrast, gray hair is often caused by factors other than the scalp environment, such as aging, genetics, or the effects of illness or medication.

Therefore, it is difficult to use hair growth treatments as a solution for gray hair.

⑤ Hair growth products can be used by both men and women

If you and your spouse are both struggling with thinning hair and are sharing a hair growth product, you should be careful. The causes of hair loss differ between men and women, and some hair growth products are not recommended for use by women who are breastfeeding or pregnant.

Therefore, unless the manufacturer explicitly states that a product is “for both men and women,” it’s best not to share it lightly. Since there are now many hair growth products designed specifically for women, we recommend that women use a product intended just for them.

What did you think? Did any of this surprise you? While various theories are circulating, most seem to lack scientific basis. Let’s focus on anti-aging through a balanced diet, moderate exercise, and adequate sleep.