Views: 3 Author: Site Editor Publish Time: 2022-08-12 Origin: Site
Why we need sun protection?
The length of telomeres at the ends of our chromosomes determines, to a certain extent, our human lifespan. Because every time a cell divides, the telomeres at the top of the chromosomes shorten once. When the telomeres can no longer be shortened, the cell will not continue to divide. At this time, the cell will reach the generally considered limit of 100 divisions and begin to die. Telomeres are located at the ends of linear chromosomes and are rich in tandem repeat sequences. Our human telomere structure is (TTAGGG)*n. With the increase of cell passages, the length of telomeres gradually shortens. Cell telomeres are shorter than young individuals, so telomeres are biologically regarded as molecular markers of cellular aging.
If we are exposed to high-intensity ultraviolet rays every day, in order to ensure that the DNA is not damaged, the telomeres will absorb the energy of ultraviolet rays, which will also shorten the telomeres. Studies at home and abroad have shown that since DNA is the main target of UV-induced cell damage, natural aging and photoaging can ultimately shorten telomeres through different mechanisms, thereby causing a series of changes related to aging.
What is UV?
Ultraviolet rays are rays of light with a wavelength of 10 to 400 nm in sunlight. In rough terms, it can be considered that the ultraviolet rays radiated by the sun include UVA, UVB, and UVC.
UVA wavelength is 320-400nm, long wavelength, it has strong penetrating power and can penetrate most transparent glass and plastic. More than 98% of the long-wave ultraviolet rays contained in sunlight can penetrate the ozone layer and cloud layer to reach the earth's surface. UVA can reach the dermis layer of the skin, destroy elastic fibers and collagen fibers, and tan our skin.
UVB wavelength is 280-320nm, medium wave. Its shorter wavelength will be absorbed by transparent glass. Most of the medium wave ultraviolet light contained in sunlight is absorbed by the ozone layer, and only less than 2% can reach the earth's surface. Especially strong. UVB ultraviolet rays have an erythema effect on the human body, which can promote the metabolism of minerals and the formation of vitamin D in the body, but long-term exposure will cause redness, swelling and peeling of the skin.
UVC wavelength is 100-280nm, short wave, its penetrating ability is the weakest, and it cannot penetrate most transparent glass and plastic. The short-wave ultraviolet rays contained in sunlight are almost completely absorbed by the ozone layer. Earth's ozone layer blocks 97-99% of UV radiation that penetrates the atmosphere. 98.7% of the ultraviolet rays reaching the earth's surface are UVA. UVC and higher energy radiation contributes to the production of ozone and forms the ozone layer. Among them, UVA is the most carcinogenic, and the effect of sunburn and sunburn is 1000 times that of UVB. UVC is generally blocked by the ozone layer.
In recent years, more research has been done on infrared-induced skin problems. IR (Infrared) is infrared rays that can cause sunburn, microvascular dilation, dermatitis, and promote the carcinogenicity of ultraviolet rays.
The principle of sun protection
For the vast majority of people, sun protection is a problem that cannot be ignored, but for people with skin inflammation or pimples, acne, it is still a step by step, one problem is solved gradually, I personally think that in the In the case of obvious skin problems, applying sunscreen may be a burden, but it will be counterproductive. For example, the high concentration of alcohol in Japanese sunscreens may aggravate inflammation, and pure physical sunscreens may clog pores. At this time, pure physical sunscreens are used instead. It is more appropriate to take measures such as wearing masks, sun hats, and sun protection parasols.
There are no more than two principles of sun protection. One is physical sun protection, which achieves the effect of sun protection by reflecting or scattering ultraviolet rays. The most common physical sunscreens are zinc oxide and titanium dioxide. These two have been approved by the FDA as the first class of sunscreens. They have high safety and good stability. The disadvantage is that they will deposit on the skin surface. The so-called whitening is like this. The size of the sebaceous glands may also affect the secretion of sebaceous glands, causing blockage.
The other is chemical sunscreen, which works by absorbing UV energy. Common chemical sunscreens include methoxycinnamate, benzophenone, p-aminobenzoic acid and its derivatives, etc. The disadvantage is that most of them are oil-soluble, so the products are relatively oily.
Therefore, in order to promote strengths and avoid weaknesses and provide comprehensive protection, the combination of physical and chemical sunscreen is also the formulation strategy of many brands.
Sunscreen plays a direct and decisive role in sunscreen. Here are some sunscreens: Octinoxate, Octyl Methoxycinnamate, OMC.
OMC is the most common UVB sunscreen on the market today and is widely used. As a UV absorber, there is a large conjugated π bond in the molecule of OMC. This conjugated structure can be regarded as a benzene ring as the core, one side extends to the oxygen atom in the substituted methoxy group, and the other side extends to the other side. Double bond and ester group in one substituent. This conjugated structure determines that the substance has the property of absorbing ultraviolet rays. OMC can absorb ultraviolet rays in the wavelength range of 280-320nm, and has a maximum absorption at 311nm, so it has a good protective effect on UVB, and has high absorption rate, good safety, and oil solubility, so it is widely used in daily chemicals, plastics, rubber. As an oil-soluble liquid UVB absorber, it can be compounded with various sunscreens. The toxicity is extremely small and relatively safe. Animal experiments believe that it may affect the effect of estrogen, and the concentration limit is 10%.
Avobenzone, Parsol 1789, Butyl Methoxydibenzoylmethane
Avobenzone is a main ultraviolet UVA sunscreen agent, which can absorb UVA 320-400nm band and block some UVA-I, but has weak effect on UVA-II, and the maximum absorption wavelength is 357nm, so it is often combined with benzophenone. -3 mixed use. Although it is safe, the biggest disadvantage of avobenzone is its photostability. After being irradiated by ultraviolet rays, it will be gradually decomposed and lose its sunscreen effect. Especially when it is combined with Octinoxate (OMC), it can increase avobenzone, photo-instability, thus reducing UVA protection time.
Avobenzone reacts with minerals to form colored complexes, which have dyeing properties and can dye clothes, so try not to touch them. Avobenzone was patented in 1973 and approved in the European Union in 1978. Approved by the FDA in 1988. Its use is recognized worldwide. In order to stabilize its photostability, many companies usually cooperate with other UVB components to stabilize the system, such as Neutrogena's Helioplex technology. In addition, L'Oreal and other groups also have related patents.
Helioplex, which achieves superior sun protection by effectively stabilizing UVA and UVB absorbers -butylmethoxydibenzoylmethane (Avobenzone) and benzophenone-3 (Oxybenzone), has been certified by the U.S. Food and Drug Administration as a Safe and effective sun protection technology.
Avobenzone is an absorber of UVA, and Oxybenzone is a good absorber of UVB, and can absorb part of UVA, but usually Avobenzone is very unstable in the sun, and continuous sunlight exposure will reduce its UVA blocking effect, so ordinary sunscreens. The sunscreen effect does not last long. Helioplex, on the other hand, effectively combines Avobenzone and Oxybenzone, making the two absorbent components complementary and stable in the sun for extended periods of time, providing a more comprehensive sunscreen effect. It can be seen that Helioplex sunscreen technology can help to filter UVB burning rays for a long time, while effectively preventing UVA damage to the skin on the surface, and providing the best protection deep inside the cells.
Oxybenzone, Benzophenone-3, BP3
BP3 is a sunscreen with a high risk index. It can absorb UVB and some UVA bands. It is oil-soluble. In recent years, there has been a lot of controversy about changing sunscreens. When the concentration is below 5%, the sunscreen effect is general, but BP3 may induce photosensitivity. Absorbed by the skin in large quantities, it is allowed to be used in the European Union, and the dosage should not exceed 6%. Pregnant women avoid use.
There are similar UVB sunscreens such as BP4, BP5 and BP9, which are toxic and irritating to human skin in excess.
Octocrylene, Octocrylene Cyanate, OCR
OCR is also relatively common. It is an oil-soluble spectrum UV absorber, which can absorb UVA and UVB in the middle band of ultraviolet rays in the range of 250-360nm. It is often used together with other sunscreens in sunscreens because of its high absorption rate, non-toxic and non-toxic. It has good stability to light and heat, and can achieve high SPF sun protection index, but Octocrylene will release oxygen free radicals when exposed to sunlight. FDA approved for use.
4-MBC is an ultraviolet UVB sunscreen. China, Australia, and Japan allow it to be added to sunscreens, but the US FDA does not allow it. European studies believe that 4-MBC is toxic to the thyroid gland and interferes with human hormones. The required dosage should not exceed 4%.
Homosalate, Methyl Salicyl Alcohol, Isooctyl Methoxycinnamate
Homosalate is an ultraviolet UVB sunscreen that can absorb the 295-315nm band, but studies have shown that Homosalate has a weak effect on hormones and produces toxic metabolites, and the required dosage should not exceed 10%.
Ensulizole, Phenylbenimidazole Sulfonic Acid
Ensulizole is an ultraviolet UVB sunscreen agent, which can also absorb a small part of the UVA band. It is a water-soluble chemical sunscreen agent.
Cinoxate is also called ethylhexyl methoxycinnamate. Cinoxate is an ultraviolet UVB sunscreen agent, which is a chemical sunscreen agent. It is not widely used, and there are not many related research reports.
Isopropyl methoxycinnamate, isoamyl methoxycinnamate
Isopropyl methoxycinnamate is an ultraviolet UVB sunscreen agent, which is a chemical sunscreen agent. It has been approved for use in the European Union, but Japan prohibits its use with some specific ingredients.
Octisalate, Octyl Salicylate
Octyl salicylate has a conjugated π bond, which can absorb ultraviolet rays and convert the energy of ultraviolet rays into heat to release the sun to achieve the purpose of sun protection. Octyl salicylate can absorb ultraviolet rays in the 280-300nm band and is used as a UVB absorber In sunscreen makeup, although octyl salicylate has less UV absorption capacity, it is safer, less toxic, and less expensive than most other sunscreens, so it is a type of UV absorber that people use more often.
Uvinul A Plus, Diethylaminohydroxybenzoyl Hexyl Benzoate
Uvinul A Plus is a good UVA sunscreen, also labeled as Diethylamino Hydroxybenzoyl
HexylBenzoate, approved for use in sunscreens in Australia, but not approved by the US FDA, requiring no more than 10%.
Ethylhexyl Triazone, Uvinul T 150
Ethylhexyl Triazone is a product of BASF, Germany, and Uvinul T 150 is the product name of BASF's raw materials. Uvinul T 150 is a UVA sunscreen agent that is allowed to be used in sunscreens in the European Union, Australia, and Japan, and the dosage should not exceed 5%. Because studies have shown that long-term use of Ethylhexyl Triazone will affect the water environment, the US FDA has not approved its use.
Tinosorb S, Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine
Tinosorb S is a new type of broad-spectrum sunscreen agent, which often appears in the ingredient list: Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine, Tinosorb S is a trade name, developed and registered by Swiss Ciba Company. Tinosorb S can absorb both UVA and UVB. It is an oil-soluble chemical sunscreen with good photostability and no estrogenic activity. It has been approved by the European Union. The sunscreen band is very broad, the maximum absorption peak is at 342nm, and after 370nm, the absorption is poor. Tinosorb S has a high absorption efficiency, and a small amount of it will have a good effect of improving the sunscreen ability. It can also effectively stabilize avobenzone, and it will not be destroyed by other ingredients (such as OMC).
Tinosorb M, Methylenebis-benzotriazolyl tetramethylbutylphenol, Tenrais M
Tinosorb M, the brother of Tinosorb S, belongs to the Swiss company Ciba. It is a water-soluble UVA protectant. It is a large organic particle molecule that can be dissolved in the water phase. It has high stability. It can not only absorb and convert ultraviolet rays, but also has a certain The function of reflecting and scattering ultraviolet rays, the sunscreen band is also very wide. For long-wave UVA, especially in the 380-400nm range, it belongs to the dead zone of any other sunscreen, but Tinosorb M can still maintain part of the absorption characteristics. It can be used together with Tinosorb S. Make up for the weak absorption of Tinosorb S after 370nm.
Neo Heliopan AP, disodium phenyldibenzimidazole tetrasulfonate
Neo Heliopan AP is a water-soluble UVA sunscreen agent, photostable, permitted in Australia, and the dosage should not exceed 10%.
Mexoryl SX, terephthalmethylene dicamphor sulfonic acid, wheat color filter SX
Mexoryl SX was patented by L’Oreal Group in 1982 and approved by the European Union in 1991. It is a water-soluble chemical sunscreen that can resist ultraviolet wavelengths in the range of 290~400nm, and the maximum absorption peak is at 345nm. It was approved by the FDA in 2006.
Mexoryl XL, Trazole Trisiloxane Cresol, Wheat Filter XL
Mexoryl XL, the twin sister flower of Mexoryl SX, also belongs to the L'Oreal Group. It was introduced at the European Dermatology Conference in 1998. It is an oil-soluble broad-spectrum UV absorber with two absorption bands at 303nm and 344nm. Mexoryl XL is light stable, water and sweat resistant, and is often used with Mexoryl SX because of their synergistic effect in protection.
Titanium Dioxide, Titanium Dioxide, TiO2, CI77891
Titanium dioxide is an excellent physical powder sunscreen agent. It blocks ultraviolet UVB and part of UVA by means of reflection and scattering. It is hardly absorbed by the skin, so it is very safe. However, when the concentration exceeds 5%, it can completely block ultraviolet UVA. , Because it belongs to the category of pigments, it must be added at a high concentration to achieve a better sunscreen effect, which is why it will turn white when applied to the skin, plus its high oil absorption and water absorption characteristics, it is easy to cause dry skin. In order to improve the use feeling and sunscreen effect of titanium dioxide, it is usually made very fine, but ultra-fine titanium dioxide does not reflect but absorbs ultraviolet rays, and has strong photocatalytic activity, so the process of titanium dioxide particles , Encapsulation technology, will lead to the sunscreen effect and feeling of use vary widely.
Zinc Oxide, Zinc Oxide, ZnO
Compared with titanium dioxide, zinc oxide has a wider range of UV wavelengths than titanium dioxide, which can cover both UVA and UVB. Titanium dioxide-based sunscreens are strong against UVB, while zinc oxide is better at UVA. Similarly, zinc oxide not only absorbs oil, but also absorbs moisture, which can cause dry skin after use. Zinc oxide can be used as a white pigment, so whitening on the face is inevitable.