The weather has been so hot lately that it’s like a sauna: hot, stuffy, hot… I’ve been soaked in sweat once I go out.
So the thing I want to hear outside is: Roll and cool off.
But, the hot sun, in addition to being hot enough to sweat profusely, will also tan and burn people in minutes, causing temporary discomfort to the skin. In severe cases, it may cause long-term damage to the skin. even lead to skin cancer.
And these two guys are making waves on human skin: Ultraviolet A (UVA) and Ultraviolet B (UVB) ).
UVA:Wavelength 320nm-400nm, it can reach the dermis, indirectly damage DNA, promote photoaging, affect pigmentation, and May be involved in skin carcinogenesis.
UVB:The wavelength of 290nm-320nm can pass through the stratum corneum and epidermis, directly causing DNA damage, causing sunburn, Inflammation, hyperpigmentation and photocarcinogenesis.
Seeing this, I know why we emphasize sun protection again and again. In order to avoid the attack of ultraviolet rays on the skin, various sun protection “weapons” are required, among which sunscreen is one of the classic means.
Speaking of this, Xiaohong wants to say a few words, don’t laugh at yourself for being too lazy to apply it every day, and boys say “sunscreen, whoever uses this shit”. You sunscreen or not, you will definitely see the difference in the future.
The question is, what do you want to know about buying a sunscreen?
What is the SPF value? How many + does PA have? Chemical sunscreen or physical sunscreen? Let’s talk more about it.
How to see SPF value?
SPF primarily measures UVB protection and is based on the ratio of minimum erythema (MED) of sunscreen-protected skin to unprotected skin.
A higher SPF value means your skin is less prone to sunburn and better protected. However, SPF is not multiplied by absorption of UVB radiation.
When applied in sufficient quantities, sunscreens with SPF 15, 30 and 50 absorb 93.3%, 96.6% and 98.0% of UVB radiation, respectively. The multiple here actually refers to protection time (I didn’t expect it, just look at the table below to understand)
Usually we recommend that you if you don’t spend much time outdoors, SPF15 is enough; if you have more outdoor activities, you can use SPF15-30 >; If you go to areas with strong ultraviolet rays such as snow mountains, plateaus, and the seaside, it is better to use SPF50+ sunscreen.
How to see the PA value?
PFA is rarely heard, only PA is known. PFA mainly measures the UVA protection ability, which is based on the ratio of the minimum sustained darkening amount (MPPD) of sunscreen-protected skin to unprotected skin.
And PA refers to UVA protection level, they are closely related, and the number of plus signs makes it more intuitive. The more PA+, the higher the PFA value and the better the ability to protect against UVA.
What? The above is too professional, can’t you understand? you can directlyThe solution is:
The higher the SPF, the stronger the anti-UVB ability, the better the sun damage; the more PA+, the stronger the anti-UVA ability, the better the ability to prevent sunburn.
What is the difference between physical sunscreen and chemical sunscreen?
At present, sunscreen products on the market are mainly divided into three types: physical sunscreen, chemical sunscreen, and physicochemical combined sunscreen.
Physical sunscreens (inorganic type) are actually very easy to recognize, nothing more than titanium dioxide (TiO2), zinc oxide (ZnO). two kinds.
There are more chemical sunscreens (organic type), and there are more than 20 kinds of ingredients approved for use in China. The most frequently used sunscreens are: octyl methoxycinnamate, Avobenzone (butylmethoxydibenzoylmethane), oxybenzone, octyl dimethylaminobenzoate, octocrylene, homosalate, and octyl salicylate, among others.
(Picture source transparent label: Yi Siding sunscreen ingredients)
Among the commonly used chemical sunscreens, benzophenones protect against UVB and short-wave UVA, and Oxybenzone (benzophenone-3) is the most commonly used in the world of UVA sunscreens.
Avobenzone can effectively protect against long-wave UVA radiation, but it is extremely unstable to light, it needs to be compounded with other ingredients to maintain stability, such as Austrian Crelin.
Wheat Filter SX and Wheat Filter XL are light-stable broad-spectrum sunscreens that absorb both UVB and short-wave UVA. Both of these can prevent pigmentation caused by UV, and the combined effect is better.
Seeing this, everyone has a lot of guesses about the ingredients of sunscreen, but I don’t know which one is better, physical sunscreen or chemical sunscreen?
Come on, one picture will show you easily, and you will know which one you should choose.
In addition to the above two sunscreens, you may have heard of biological sunscreen, and it sounds like a new type of sunscreen.
In fact, it is a class of bioactive substances based on vitamin C, vitamin E, niacinamide, glutathione, beta-carotene, which can resist UV radiation, but does not absorb, so is generally not considered a sunscreen.
If such ingredients are compounded in sunscreen products, there are two main functions:
Protect active ingredients in products, such as sunscreens, through antioxidant action.
Use its own effects such as whitening spots, reducing fine lines, etc.
However, don’t expect the superposition of its effects to be excellent, After all, it is a hooligan to talk about efficacy without concentration.
Don’t go away, do a little research:
[References]
[2] Liu Wei et al. Editor-in-Chief. “Dermatology and Evaluation of Cosmetics Efficacy”