Looking at the left side of this picture, we can see that the human body is actually 70% water. If it is a A person of 100 pounds is equivalent to 70 pounds of water in the body. There is a data surface, the maximum amount of water a person can emit through the skin in a day is 10L! span>

Our keratinocytes are like a sink, it has a water inlet, that is, the water in the body will pass through the dermis to the keratinocytes At the same time, a large amount of water will flow out into the air.

So what we have to do is to maintain a dynamic balance. If the water in and out can be kept the same, our skin You can achieve normal moisturizing.

For skin, the water inlet is aquaporinAQP3, it stays under the epidermis (stratum corneum, basal layer, granular layer, all have this protein). The dermis has a lot of water (can reach hundreds of more than 80/80), this water slowly passes through the aquaporin and is transported up to the keratinocytes. This channel is unchanged.

There are two situations when water is replenished from outside the skin. One is that water penetrates into the skin. But the stratum corneum itself It is relatively resistant to water, so most of the water applied on the skin runs into the air, and only a small part can get into your skin.

Consider increasing the rate of water inflow. There are many products that claim to increase cellular aquaporin. However, , First, this is more difficult. The product must first pass through the barrier of the skin's stratum corneum and reach the cells below to function. Second, this will actually require a relatively high cost. Then, there is actually a more cost-effective method, that is Decrease the rate of water output.

Our skin thinks the same way. It has three gates at the water outlet to prevent the water from running too fast.

The first gate, there is a natural moisturizing factor NMF in our keratinocytes (Fig. The blue origin), it helps the cells catch water in the cell. The second gate is the lipids between cells (the light blue part), the familiar ceramides, cholesterol and free fatty acids. There is also a gate, It is the sebum secreted by the outermost sebaceous glands of the skin. Through the combined action of these three layers, the rate of water loss from the stratum corneum can be reduced.

The picture shows the composition of a natural moisturizing factor. It mainly contains a large number of amino acids,PCA, lactate urea, and sodium salt potassium salt and the like. Its effect is equivalent to turning the water inside the skin into saline, so the speed of water loss It will be slower than fresh water. The small water molecules in it can catch water, can also make water molecules run slower. However, this is not enough.

Even if it is saline, it will dry out if left in the sun. So it is necessary to fill the cells with lipids .

We often say that keratin is a city wall, a structure of bricks and cement. Bricks are keratinocytes, Cement is the lipid between cells. The lipid is mainly a combination of ceramides, free fatty acids and cholesterol.

Lipids must be stored in the basal cells and granular layer cells, and when the granular layer cells become keratinocytes, These lipids are spit out from the cells to coat the cells and help reduce water loss.

The interskin lipids have a very sophisticated structure and are difficult to replenish. span>

Substances such as ceramides are not only expensive, but also difficult to dissolve and further enter the skin. Some products have For such technology, for example, there are many ceramide products that can replenish the lipids between the skin and repair our skin barrier, which is very good. But there is a simpler and cruder method that we most commonly use, It is to work on the outermost layer.

In the outermost layer, the skin has sebum secreted by the sebaceous glands. p>

Sebaceous glands and hair follicles share the same outlet, which is our pores. It secretes sebum mainly including triglycerides, cholesterol, squalene and wax fat. Also, our sweat glands are another separate opening. Our sebum and sweat glands mix together to make up our sebum membrane, which forms our protective layer on the outside of our skin.

The normal skin moisturizing practice is to use oil on the skin. Creams and lotions will contain oil. However, in the end What is a good oil? Many people have the question, will using too much oil clog pores and cause blackheads and acne? The choice of oil should basically be in two directions.

First, the oil used is not friendly and incompatible with the sebum of the skin. It will not enter the skin if it stays outside. Hair follicles block pores.

This kind of grease, such as silicone oil, mineral oil. People will be more repulsive to chemical things, but in fact it depends on the actual situation Situation. Oils such as silicone oil or mineral oil are not friendly to sebum, they can act as a good seal on the outside of the skin and keep water out. At the same time, they are not easy to penetrate into the skin and make the skin feel uncomfortable.

The second type of oil, it is very friendly to your sebum and will not cause all kinds of irritation or blockage.< span>

For example, squalene and wax grease unique to our cortical membrane, many products like to use this kind of grease. Squalane can be turned into squalene on the skin, which is the same ingredient as the cortex. Wax is rarely found in nature. Here we should mention jojoba oil, which is very similar in structure to wax and can be very good. Penetrates well into the skin without irritating the skin.

Other oils like isopropyl palmitate, isopropyl myristate. They have some affinity with sebum, so It is easy to get into the pores of the skin. But they are not exactly the same structure as the sebum of the skin, so that the skin may not recognize them after entering. At this time, the pores will lose their temper, causing acne, fans and the like. Of course , it also depends on the amount of these oils contained in the product. If it is a small amount, it may not necessarily cause problems. Moreover, the occurrence of these conditions varies from person to person, and more often you have to try it yourself. span>

Finally, let’s talk about natural oils.

Although these oils have different names, they are actually relatives. They are all fatty acid glycerides, but the fatty acids in them The ratio is different.

Coconut oil is a skin care oil that is often mentioned. It can be seen from the table that it contains high lauric acid. Lauric acid is the kind of thing I just mentioned that likes to drill into the pores. Therefore, coconut oil may cause closure and acne in some people, and it is not a good skin care oil.

And then like olive oil, it has a lot of unsaturated fatty acids (such as oleic acid, linoleic acid, linolenic acid), which can Antioxidant. However, it also has a high content of oleic acid. Oleic acid likes to drill into the lipids between skin cells, which is the structure formed by the ceramides, cholesterol and free fatty acids we mentioned earlier. It is neat and can block the water. At this time, the oleic acid drills in and disperses the formation, and the water takes the opportunity to run away. Therefore, the high content of olive oil will weaken the skin barrier, and it is not a particularly good skin care. Oil.

You can use oils like rosehip oil and grapeseed oil on the skin, but better The method is to eat it in. Because the production of lipids between the skin requires the participation of unsaturated fatty acids necessary for the human body, that is, linoleic acid and linolenic acid. The source of these raw materials is mainly what we usually eat. After we eat it, blood vessels Send it to the dermis, and then from the dermis to the epidermis to supply epidermal cells to make ceramide.

The above is mainly about moisturizing the skin. In general, you can use water to supplement the outermost part, But the supplementation effect will be very weak. Now the lotion we use mainly does not rely on water, it contains a lot of glycerin, butanediol or even a lot of small molecules (such as NMF natural moisturizing factor). These Substances burrow into keratinocytes to help hold water molecules. Creams or lotions rely mainly on the oils in them.

In addition, there is a very commonly used moisturizing method - applying mask. 0 span0

The mask has the function of encapsulation, making it difficult for water to run into the air and promoting the running of water into the skin. This is true Very effective. So applying a mask usually has an immediate effect.

The keratinocytes become transparent after being absorbed, the skin becomes very bright, and people also appear white. However, using Masks also have problems. We mentioned earlier that if you soak your hands in blisters for a long time, you will wrinkle. If you keep applying the mask, too much water will suck up the keratinocytes that were originally shrewd and dry, causing them to not be able to stand guard for the skin. The permeability increases, and various pollutants in the air can easily enter. Therefore, the mask cannot be applied every day. In medical dermatology, there is a term called hydration dermatitis. It means that the skin absorbs too much water and the entire barrier function is lost. 。 At this time, external stimulation will lead to dermatitis.

In addition, it should be noted that other products, especially functional things, should be Be careful.

After applying the mask, everyone will want to take a strong medicine, such as high concentrationVC, retinol or retinol and other products. At this time, a large number of ingredients pour in, which may be harmful to the skin. Causes irritation and leads to allergies.

There is also makeup. After applying the mask to the skin, everyone will feel that the makeup is much easier to put on, and it is not easy to take off. However, If you put on makeup at this time, cosmetics (that is, make-up) are relatively more irritating than skin care products. Therefore, it is not recommended to put on makeup immediately after making the mask.

After applying the mask to open the moisture channel, it is best to close the door as soon as possible. At this time, you should use some comparison Basic moisturizing products. Skin care products such as creams are more suitable at this time.

Another misunderstanding that everyone may have, many people think that the external humidity of the skin is relatively high in summer, just use a little water However, everyone must remember the three gates of skin moisturizing. Of course, the water you use contains substances such as glycerin and moisturizing factors. But this alone is not enough. Even in summer, it is recommended that you use some oils. You can choose some The light lotion acts as an envelope on the outside of the skin for better hydration.

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