In the minds of some people, “hair with luster and no dandruff” may only be a cosmetic requirement. In fact, “hair with luster and no dandruff” occupies a place in the ten health standards of the World Health Organization.
Recently, the South China base of the Chinese scalp health research center was established in the Third Affiliated Hospital of Sun Yat sen University. The reporter learned that more than half of adults in China have scalp health problems, of which greasy, itchy and dandruff are the most common. Dermatologists point out that dandruff is determined by sebum, Malassezia and individual susceptibility. Most people’s scalp health problems can be solved by following scientific maintenance schemes.
short hair is more likely to appear greasy
There are many sebaceous glands, sweat glands and tens of thousands of hair follicles under the healthy scalp. The number and density of hair follicles are determined at birth. There are about 100000 to 150000 hair follicles on each person’s head, and each hair follicle can grow about 20 hairs in a person’s life. After that, this hair follicle completes its “glorious mission”.
Therefore, the number of scalp hair follicles will not increase in adulthood, but will gradually decrease. Usually, there are 1100 hair follicles per square centimeter of scalp in infancy. This number drops to 600 at the age of 25, and only 250 at the age of 50. Therefore, with the growth of age, hair becomes less dense than before, which is a normal phenomenon in line with the natural law.
In the upper part of the hair follicle, there are sebaceous glands connected with it. Sebum spreads upward along the hair from the hair follicle, moistens the scalp and hair, and acts as a natural barrier to protect them, but sebum is not absorbed by the hair.
How much sebum can be produced by sebaceous glands is mainly determined by human genetic genes, but generally speaking, sebum secretion will gradually decrease with age. Experts point out that the amount of sebum produced by sebaceous glands has nothing to do with hair style.
Very short hair can be covered with only a small amount of sebum on the surface, so short hair is easy to appear more greasy. Generally speaking, the androgen level in adolescence is high, and the sebum produced by sebaceous glands increases greatly, so adolescence will have an oily scalp tendency.
dandruff and seborrheic dermatitis have the same etiology
Many people with dandruff will have such experience: once the hair is oily, it is easy to get dandruff. In fact, in addition to the perceptible factor of scalp oil, dandruff is also closely related to another factor invisible to the naked eye – Malassezia.
Xu Qingfang, associate professor of Dermatology of the Third Affiliated Hospital of Sun Yat sen University, introduced that Malassezia is a common fungal group, which feeds on the scalp with sebum secreted by the scalp. Dandruff is composed of cuticle cells of the scalp. Under normal circumstances, Malassezia and humans are at peace, and the keratinized epidermal cells of the scalp fall off individually. This process takes about 28 days. “But once Malassezia has abnormal reproduction and the number exceeds the normal level, it will accelerate epidermal metabolism. This process is compressed to 7-21 days.
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