Affected by atmospheric pollution, the ozone layer is becoming increasingly thin, and the ultraviolet energy reaching the ground is continuously enhanced. The harm caused by ultraviolet radiation to the human body has been paid more and more attention [1]. Ultraviolet radiation (UV) can cause skin burns and erythema, promote premature aging of the skin, cause keratitis and cataracts, damage immune cells in the skin, and cause systemic immune suppression. Therefore, sun protection has become a hot topic in the world. Therefore, sun protection has become one of the hot topics in the development of cosmetics at home and abroad.
1 The effect of ultraviolet light on the human body
In the dermatology world, ultraviolet rays are classified into long-wavelength ultraviolet rays (UVA) of 320 nm to 400 nm, medium-wavelength ultraviolet rays (UVB) of 280 nm to 320 nm, and short-wavelength ultraviolet rays (UVC) of 200 nm to 280 nm. Ultraviolet rays below 280 nm are absorbed by the ozone layer and cannot reach the ground. The ultraviolet rays reaching the ground will have various effects on people's skin. Among them, UVB can cause erythema or blisters on the skin, promote melanin formation, cause pigmentation of the skin, and cause brown spots. Formation. It has been previously thought that UVA does not have a large effect on the skin, but it has been proved by electron microscopy or histochemistry that excessive UVA irradiation will have a certain effect on the skin. UVA is different from UVB, and its energy can be Reaching the dermal layer of the skin, causing a slow change in the elastic fibers in the vessel wall or in the bonded tissue. Thereby causing browning of the skin, reducing the elasticity of the skin, promoting the occurrence of wrinkles, causing rapid aging, and also promoting erythema reaction or even causing phototoxicity or photosensitivity. Sensitive skin in the sun through UVB, UVA radiation can also damage DNA to reduce immunity, and even induce skin cancer. Therefore, it is increasingly important to prevent excessive UVA and UVB radiation from protecting the human body from injury and delaying aging. The addition of UVB and UVA absorbers to sunscreen cosmetics is currently an effective and widely used method. It can not only effectively prevent the skin from aging, reduce the occurrence of wrinkles and skin cancer, but also prevent the accumulation of pigmentation and the dullness and inelasticity of the skin [2].
There are various theories about the mechanism of skin aging. Bjonkster believes that skin aging is caused by the polymerization of collagen in the skin. Under normal conditions, the polymerization and crosslinking reactions proceed slowly, but under the action of ultraviolet light, the reaction speed is greatly accelerated. According to the theory of chemical reaction activation energy, he believes that ultraviolet light irradiation affects cross-linking and polymerization rate is the main factor of skin aging. The theory of free radicals believes that aging is the result of obstacles to free radical production and elimination. Under normal circumstances, generation and elimination are in a relatively balanced state. However, the irradiation of ultraviolet rays can increase the formation of oxygen free radicals. After the formation of free radicals, it can attack, infiltrate and damage the cell structure of the skin, and produce lipid peroxides in the damaged part of the cell membrane, which triggers a series of mutation processes, and finally Causes accelerated skin aging. There are many reasons for skin aging, and the mechanism of aging is not the same, but one thing is clear. Ultraviolet light irradiation is one of the most important external causes of skin aging [3].
Sunscreen mechanism of sunscreen cosmetics
Sunscreens are used for sunscreen protection in sunscreen cosmetics, and the sunscreen principle varies depending on the sunscreen added. There are several types of sunscreens added to the general formula.
One is to use a sunscreen to scatter light to provide a sunscreen effect. Such as various foundation creams, sunscreens in powder cakes, the main components are titanium dioxide, zinc oxide, talcum powder, etc., they can reflect a certain amount of ultraviolet light, so as to achieve the purpose of sun protection. The cosmetic benefit of this sunscreen is that it can prevent the damage of medium wave and long-wave ultraviolet rays at the same time. The disadvantage is that it is airtight and opaque.
The second type of sunscreen is sunscreened by its absorption of ultraviolet light (200-400 nm), which is mostly a variety of organic sunscreens, such as: A. anthranilate, which is at 338 nm. There is an absorption band; B.DOE-2 (new product of Dalian Light Industry Research Institute), its maximum absorption value for ultraviolet light is 330-340 nm; C. ethyl salicylate, which has absorption at 305 nm Optical tape. The sunscreen effect sequence of the above three sunscreen agents: A>B>C. Turn. For example, the MEXORYLSX and MEXORYLXL filters contained in the Lancome product are such sunscreens. In general, high quality sunscreen products are complex sunscreens.
Types and applications of sunscreens
Organic sunscreen
Isooctyl methoxycinnamate (OMC) is the most widely used UVB segment UV absorber in sunscreen cosmetics. The addition amount is generally between 3% and 7.5%, and is often used in combination with UVA UV absorber 1789 (the most representative high-efficiency UVA absorber) to achieve a broad spectrum or full-effect sunscreen effect. In the pure compound state, OMC has high photostability, but in the emulsion system of sunscreen cosmetics, especially in the presence of water and surfactant, its light fastness or light stability under ultraviolet light is not too good. high. The photodegradation products of OMC have a certain stimulating effect on the skin. In order to reduce the sensitivity of skin users to irritating reactions under the stimulation of sunlight after applying sunscreen cosmetics, it is usually necessary to add anti-inflammatory components such as bisabolol, aloe vera and dextran to maximize the irritant response. Reduce the irritancy of the product [4]. 4-methylbenzylidene camphor (MBC) is a UVB absorber with high photostability and high absorption efficiency, which can stabilize the UVB absorber such as OMC to some extent. The addition amount is generally 0.5% to 4%, and is often used in combination with a UVA absorbent to achieve a broad spectrum or full-effect sunscreen effect.
It is the most representative high-efficiency UVA absorbent. It is usually added in an amount of 1% to 3%. It is often used in combination with a UVB absorbent (such as OMC or MBC) to achieve a broad spectrum or full-effect sunscreen effect. Due to its molecular structure, the light stability is poor. The UVA absorber is currently the only long-wave UV absorber approved by the US FDA, and its safety in sunscreen cosmetics has passed the long-term rigorous evaluation and review by the US FDA. Avoid contact with heavy metals and Fe3+ as well as preservatives containing formaldehyde-releasing agents during production and use.
P-xylylene dicapphoric acid disulfonic acid and its salt UV absorber are a class of water-soluble UVA absorbers [5]. The absorption range is wider than that of general UVA absorbers. It has high light stability and water solubility. It can be used in combination with a variety of UVB absorbers to achieve a broad spectrum of sunscreen effects, and is more suitable for use in spray type or water soluble sunscreen products. In the past, due to the limitations of L'Oréal patents, it was only used by L'Oreal itself. At present, there are already manufacturers in the country promoting this product.
Inorganic sunscreen
Because organic sunscreens generally have low light stability or poor lightfastness, people turn their attention to inorganic compounds, more typically TiO2 and ZnO. People use TiO2 to scatter and reflect UVB (290 nm to 320 nm) and cover the skin, and use it in sunscreen cosmetics. However, the TiO2 particles used in common cosmetic formulations are larger (particle size 500 nm~ 2000 nm), the effect of sunscreen or UVB scattering is very poor, and it mainly covers the skin. As the ultra-fine TiO2 used for sunscreen, it has the best scattering effect on UVB, and it is used together with the organic ultraviolet absorber to contribute to the improvement of the SPF value of the formulation. TiO2 and ZnO are often used as sunscreens in sunscreen formulations in combination with organic sunscreens. It is difficult to achieve high sunscreen and good results when used alone.
Table 1 lists the sunscreens used in sunscreens sold in North America.
Whether the sunscreen used in the product has UVA protection
Water-resistant sunscreen SPF60MBC (5%) 1789 (3.5%) Titanium dioxide (42%), for 1789, Mexoryl SX and titanium dioxide work together
Waterproof sunscreen SPF30 benzophenone-3 (6%) OMC (7.5%) 1789 (2.5%) Titanium dioxide (2%) has a combination of 1789 and titanium dioxide
Sunscreen SPF30OMC (7.5%) Isooctyl salicylate (5%) Hydroxybenzophenone (3%) 1789 (3%) Yes, for 1789 effect
Sunscreen lotion SPF25 8h waterproof titanium dioxide (9.6%) Zinc oxide (1.5%), for the joint action of zinc oxide and titanium dioxide
Sunscreen lotion SPF15 8h waterproof benzophenone-3 (6%) OMC (7.5%) isooctyl salicylate (5%) Titanium dioxide (1.6%), for the role of titanium dioxide
The trend of sunscreen cosmetics
(1) Nanocrystallization and ultra-finening of titanium dioxide and zinc oxide, surface treatment with hydrophilic and lipophilic functional groups on the surface of the powder, and UVA shielding of nano-titanium dioxide and zinc oxide without reducing transparency The effect will be an important research direction for sunscreens. With the development of bioengineering technologies such as genetic engineering, cell engineering, and fermentation engineering, many countries have begun to use biotechnology to manufacture biological extracts that are similar in structure to the human body and have high affinity, and are added to sunscreen products. In addition, natural sunscreens extracted from natural plants will also be the focus of future research.
(2) "Whitening + sunscreen". Since most people in the East are yellow skin and have less melanin precipitation, the main purpose of sunscreen is whitening. The new trend of whitening sunscreen products is: preventive whitening combined with whitening, sunscreen, maintenance and repair; whitening sunscreen is not only to prevent skin from producing spots, roughness, aging and blackening, more for permanent Leaves skin healthy and keeps skin healthy.
(3) Launched children's sunscreen products. Studies have shown that: If a person starts using sunscreen from a child until the age of 18, the incidence of skin cancer will be reduced by 70%. At present, the children's sunscreen market has accounted for about 10% of the entire sunscreen market, and will show rapid growth.
(4) Products that are both sunscreen and cosmetic are gradually showing their market potential to protect the skin from UV rays while modifying the complexion. Representative brands are: Estee Lauder, Clarins, Helena, Heathley and Nivea.
(5) Hair sunscreen products have begun to attract more attention, and many professional brands have launched sunscreen hair care series. Representing brands such as L'Oreal.
(6) SELF-TANNING (automatic tanning products) is becoming the mainstream development trend of sunscreen products, including creams, powders and sprays, all of which have good moisturizing properties. Representative brands such as LANCASTER/COPPERTONE.
The sunscreen cosmetics industry is full of vitality, and sun protection will be a long-term topic around modern cosmetic technology and market development.
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