Consequences of skin dehydration
The cuticle is dry, flaky and chapped, and keratinization is accelerated.
Transparency and roughness decrease,
More easily stimulated.
accelerated ageing
The function of moisturizing is to keep moisture on the skin, so as not to lose it too quickly. Moisturizing is more than just applying moisturizing cream. In fact, the skin itself has a perfect moisturizing system, and its working principle is like a water conservancy project:
Four secrets of moisturizing, dry skin is fearless
The above picture shows the principle of moisturizing:
The dermis is the source of water, which is the reservoir. Dermal interstitial cells store a lot of water. Without interstitial cells (collagen and hyaluronic acid), the water retention capacity of dermis will decrease.
Epidermal intercellular substance and NMF suck water from dermis like water pump, and moisten epidermis (especially stratum corneum).
Sweat is mixed with sebum secreted by sebaceous glands and natural moisturizing factor (NMF) to form a moisturizing membrane (sebum membrane) to prevent water loss.
Pay attention to the self-moisturizing ability of skin
Under normal circumstances, the skin has the ability of self-moisturizing, which is mainly completed by the skin barrier (i.e. stratum corneum+sebum membrane). When the environment is too dry, or the barrier function is damaged, the water loss rate of the skin will be accelerated, the water content of the stratum corneum will be reduced, and the skin will be dry and peeling. So the basic starting point of moisturizing is to maintain and protect the skin barrier function. Excessive use of the following methods may lead to a decrease in the skin's own moisturizing ability (weakened skin barrier function):
Remove excessive natural oil from skin: for example, use too hot water and cleansing products with strong cleaning power, especially soap-based products. Dermatology often uses the method of removing excessive oil to make dry skin model.
Excessive cleaning methods (such as rubbing sand, cotton pad or sponge cleaning) and frequent makeup removal;
Wash your face too often, for example, wash your face more than twice a day, and wash it hard every time, and the V-zone care of mixed skin is not in place;
Excessive exfoliation, such as the use of salicylic acid, fruit acid, tears mask products, resulting in thinning of the stratum corneum;
Too many masks: one mask a day, or more than 20 minutes at a time, or even one mask a night.
When the skin's own moisturizing power is not enough to keep moisture, the skin will feel dry, so it is necessary to use moisturizing skin care products (usually milk and cream) to help moisturize.
Tip: moisturizing dictionary
■TEWL: Transepidermal water loss rate, also known as transdermal water loss rate, refers to the speed of selecting moisture in unit time after water passes through epidermis. The greater the TEWL, the more water is lost per unit time, and the weaker the skin's moisturizing ability.
■NMF: natural moisturizing factor, a water-soluble compound composed of some amino acid residues and sodium pyrrolidone carboxylate. NMF can combine with the moisture in the stratum corneum, and maintain the moisture between keratinocytes by regulating and storing moisture, so that the skin naturally appears moist. Excessive cleaning will lead to the loss of NMF and the decline of skin's own moisturizing ability.
■ Epidermal intercellular substance: the substance that fills the gap between epidermal cells, which is composed of fatty acid, ceramide, cholesterol and sphingosine in a fixed ratio and precise structure. It is the living environment of epidermal cells, which has excellent moisturizing effect and can prevent water loss. Excessive cleaning and epidermal damage will lead to the loss of intercellular substance, worsen the living environment of skin cells and reduce the moisturizing ability.
In autumn and winter, due to the change of environment and the decrease of sweat gland secretion and sebum secretion, the skin's own moisturizing ability decreases, so moisturizing becomes more important (although it is dry in the north, it is equally important in the south).
Four most important skills of moisturizing.
1. Moisturizing: Protect the skin as much as possible, give full play to the skin's own moisturizing ability, and make this water conservancy project work normally.
The main principles are not to damage the skin, not to excessively clean the skin, to protect the health and vitality of the dermis and epidermis, and to ensure the water-containing ability of the skin itself (avoiding the above inappropriate skin care methods will soon see the effect).
Apply moisture
A good moisturizing skin care product should contain certain humectant (hygroscopic agent), grease (sealing agent) and emollient in the formula, or use the above ingredients to cooperate with each other to achieve a comprehensive moisturizing effect.
The hygroscopic agent is helpful to absorb water from the dermis layer to the epidermis layer, and can also absorb water from the air to the skin under the condition of high air humidity.
The function of sealing agent is to form oil film and reduce water evaporation. The oil with the strongest sealing ability is vaseline, followed by light mineral oil and vegetable oil.
Emollients can make skin smooth and soft.
Tip: Several ingredients commonly used for moisturizing.
■ Absorbents: glycerol (glycerol), sodium hyaluronate, butanediol, propylene glycol, etc. , responsible for pumping water;
■ Sealing agent: vaseline, mineral oil (liquid paraffin) and various vegetable oils, which are responsible for water locking;
■ emollients: lanolin, silicone oil, some esters, alcohol, etc. (Some emollients also absorb moisture), which is responsible for producing a good skin feeling;
The new trend is to use bionic preparation, and pay attention to the supplement and integrity of skin cell matrix and the activation of skin cells. Therefore, many brands begin to choose the components with biochemical activity that skin needs to add to moisturizing products, and enhance the moisturizing power of skin by simulating cell matrix, such as ceramide and cholesterol. Products using these components are usually expensive, but they are worth choosing.
Although some ingredients are not moisturizers, they can improve the condition of dermis and keep skin moist by external application, which is especially worth choosing, such as:
■ vitamin c and its derivatives;
■ lipoic acid
■ hydroxyproline
■ Whole soybean extract
■ Collagen peptide
■ Angelica extract, etc
Tip: Can the mask moisturize?
The mask will be washed off in a short time after use. Most masks use little oil, and the instant hydrating effect is good, but the moisturizing ability is weak. It is not appropriate to moisturize by mask. Cream and milk moisturizing products should be used.
Tip: What is the difference between macromolecular and micromolecule humectants?
Macromolecule and micromolecule are not a strict standard concept. Polymers are substances whose molecular weight is usually above 5000 or 10000.
Commonly used polymer moisturizing ingredients include:
High molecular weight sodium hyaluronate, collagen, tremella polysaccharide or other mucopolysaccharides, polyglutamic acid (PGA), chondroitin sulfate, some cellulose and natural colloid. Sodium hyaluronate is the most commonly used one.
Because these substances contain more hydrophilic groups, they can be combined with a large amount of water to play a role in moisture absorption and moisture retention. Because of its large molecular weight, it will be sticky, film-forming and weak in permeability. Because of its film-forming property, it can block other substances distributed in it and is not easy to penetrate. From this perspective, other nutrients can be prevented from being absorbed by the skin.
Viscous macromolecular components are more suitable for making cream products, and these products are also more suitable for use after the essence plays a moisturizing and slow-release role.
Small molecule wetting agents include various polyols (glycerol, propylene glycol, butylene glycol, etc. ), sodium pyrrolidone carboxylate (PCA-Na), calcium pantothenate (panthenol), water-soluble ceramide, sodium lactate, etc.
Small molecule wetting agent has small molecular weight, strong permeability and low viscosity. Calcium pantothenate and ceramide have important physiological activities, which can easily penetrate into cells and play a role in moisturizing. PCA-Na and sodium lactate are the components of natural moisturizing factor (NMF).
Hyaluronic acid with molecular weight less than 500,000 is also considered as low molecular weight hyaluronic acid. Moisturizing water and essence are added with small molecular components to provide a fresher skin feeling.
In practical application, macromolecular and micromolecule humectants are basically used together to achieve better moisturizing effect. For example, sodium hyaluronate Na-HA combined with glycerol has a better moisturizing effect than Na-HA alone. It is unlikely that all brands will use a single macromolecular humectant or a single micromolecule humectant. Of course, a certain category or ingredient may be highlighted in marketing promotion.
Tip: Is the propaganda of direct dermal hydration credible?
The water content of skin is more than 70%, and it is very large, and its source is drinking water. Applying 1.4ml moisturizing product to face every day can't satisfy the appetite of dermis.
Because the basement membrane of epidermis will prevent substances with molecular weight >: 40,000 from entering the dermis, macromolecular humectants such as hyaluronic acid are unlikely to penetrate the epidermis into the dermis, and other small molecular humectants have limited significance even if they penetrate. If you quickly penetrate to the point of "direct access", it will definitely cause obvious stimulation, which I believe you can't accept. Therefore, it is not necessary to see that the humectant is absorbed into the dermis through the skin.
What really lacks water is the epidermis. Therefore, the key point of hydrating and moisturizing should also be the epidermis: sufficient epidermal intercellular substance and stratum corneum with moderate water content, so as to maintain the integrity and health of the epidermis, prevent cracking and prevent excessive loss of water from the dermis, and achieve the ideal moisturizing goal.
Usually, moisturizing products consist of moisturizing water, moisturizing essence, moisturizing milk or cream. If you don't know how to read the ingredient list, in order to know the moisturizing performance of each product, you can apply this product directly after washing your face and feel how long it will make your skin feel relaxed. The longer the better.
It would be better if you can prepare a resistance skin moisture tester, but you should pay attention to the use skills:
Generally, the skin on the inner side of the upper arm is selected for experiments, and a skin area with the same properties is divided into two parts, one part is coated with moisturizing products, and the other part is not coated;
Only one product can be applied;
The skin moisture content was measured at 30 minutes, 1 hour, 2 hours, 4 hours, 6 hours and 8 hours respectively. Test the uncoated area first, then test the coated area, and take the average as the result. Generally, the moisture content of stratum corneum of young people should be above 25%, and about 30% is ideal.