【Yami Open Class|Live Content (9)】

Lesson 3: Sunscreen Whitening (Physical, Chemical Sunscreen)

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“We have done these days What???”

Before, we shared a lot of dry skin care products of [Yan An Tang] in the sun list

9From September 26th to September 29th, [Yan An Tang] was brought to the WeChat group of Yami Skin Care Open Class

1 hour a day The most scientific skin care basics

Full of dry goods

The editor of Yami will organize the content of the live broadcast and share it with those who are too late to listen to the live broadcast~

---The main topic is coming---

After understanding these values, how can I further choose a sunscreen product suitable for my skin? Here we will talk about sunscreen agents, which are also sunscreens. The most important part of a product.

Sunscreens generally fall into two categories: physical sunscreens and chemical sunscreens.

There are generally two types of sunscreens for physical sunscreens, namely titanium dioxide (titanium dioxide) and zinc oxide. First of all, they are two minerals, not It dissolves but is suspended in the sunscreen as particles.

The effect of titanium dioxide and zinc oxide on ultraviolet rays is not to rebound but to absorb. They have a strong mineral structure, after absorbing ultraviolet rays, their own It will not be damaged in any way, and the energy conversion will be released in the form of electromagnetic waves that are harmless.

Chemical sunscreen is a situation that kills one thousand enemies and destroys eight hundred. It will also happen by itself after it absorbs ultraviolet rays and converts them into release. Degradation.

Therefore, physical sunscreen has the following advantages over chemical sunscreen.< /p>

First, physical sunscreens are very stable, which has an advantage in reducing reapplication. Second, physical sunscreens are milder and It is in an insoluble state, so it is unlikely to penetrate our skin barrier and enter the body to cause irritation. At the same time, what are the disadvantages it brings? For example, titanium dioxide can reflect a lot of visible light, so it looks very white (it is the largest The use of scale is mainly in the paint we paint the walls). So with these physical sunscreen products, the face appears very white and looks very unnatural. p>

In addition, physical sunscreens are easy to rub, because they contain powders and solids. Also, their water resistance is relatively poor, and it is easy to It is not washed evenly. If you sweat, it is easy to form strips and become uneven. Therefore, you need to reapply after sweating a lot with these products. p>

Chemical sunscreens are basically the opposite of physical sunscreens. Most of them are oily or water-soluble, so they won't turn white or muddy. .Since most of them are oily, it will also have better water resistance.

The disadvantage is that chemical sunscreens will photodegrade after absorbing ultraviolet rays, which is unstable. Therefore, it needs to be reapplied after a period of time, otherwise it cannot be Acts as a sunscreen. The general idea is to reapply every two hours.

The larger molecules of some chemical sunscreens do not easily penetrate the skin, while some chemical sunscreens with small molecules can easily enter the skin , causing irritation to the skin.

After talking about the advantages and disadvantages of physical and chemical sunscreens, let's Look at the different sunscreens in detail.

First look at physical sunscreens, titanium dioxide (titanium dioxide) and zinc oxide. The above picture shows the absorption of ultraviolet rays by the two substances. Titanium dioxide The absorption is mainly UVB, yesUVB has stronger defense. Zinc oxide is relatively resistant to UVA absorbs better, while UVB span>There is also a certain amount of absorption, which is relatively average. Therefore, if a pure physical sunscreen product only uses titanium dioxide, then its PAwill not be very high, and the tanning ability is not good.

Someone will ask, Su Yan cream orBBThe formula of the cream also contains titanium dioxide, so is it enough to use them for sun protection? p>

The answer is no.

Theoretically, if you make the particles nano-scale (visible light can be bypassed), it will appear transparent. So, For the titanium dioxide used in sunscreen products, relatively small particles are generally used, and we hope that the smaller the particles, the better, so that the sunscreen will not appear white.

No Tone Cream works to whiten your skin.BBThe cream has different colors, but titanium dioxide is also added first (equivalent to needing to paint on white paper). The particle size of titanium dioxide in them It is very large, because the bigger it is, the easier it is to cover and white. The titanium dioxide content is actually very low. If the product used contains 1% The large particles of titanium dioxide can already make the face very white. For sun protection, we may add the content of titanium dioxide to 5%-6%, or even 10%-20%. So, no makeup cream and BB The amount of titanium dioxide in the cream is not sufficient for sun protection.

Here I will show you two examples, the sunscreen for sensitive skin and the small blue bottle for sunscreen Sensitive skin and children's sunscreen have greater requirements for mildness, so pure physical sunscreen is generally used. Here you can see that the sunscreens contained in these two types are only titanium dioxide and zinc oxide. Of course, some people complain These two types are too white to be applied on the face. Here is an example for everyone.

Next, I want to talk about chemical sunscreens that are more commonly used now.

There are fewer choices of physical sunscreens, and it is more difficult to achieve higher SPFvalue. And chemical sunscreens can do itSPF50 evenSPF100.

So how to choose a chemical sunscreen that is suitable for our skin? Here are mainly divided into preventionUVAand antiUVBTwo.

AntiUVBChemical sunscreens are more common and have better stability. Anti-UVAUVASunscreens are usually not very stable to light. The first one used is butylmethoxydibenzoylmethane in the picture, usually we call it avobenzoneAvobenzone, it is a common anti-UVA span> sunscreen.

At that time, for anti-UVAFew sunscreen options. Avobenzone absorbsUVA is very strong, but its biggest problem is that it is very unstable, which is what we call dead. It absorbsUVABut it will be degraded very quickly. To maintain its stability, the most used products are ocrelline and dipendone span>-3, these two ingredients can help avobenzone degrade less quickly So, everyone should pay attention that if the product only contains avobenzone without the ingredients that help it stabilize, this means that this sunscreen product needs to be reapplied frequently.< /span>

Another thing to be careful about is that there is another commonly used UVBSunscreen - ethylhexyl methoxycinnamate. This ingredient and avobenzone can promote the decomposition. Therefore, Be very careful if you have a product that uses both ingredients at the same time, it will degrade very quickly and require frequent reapplications. Of course, product design will try to avoid both ingredients at the same time.< /span>

Here I will talk about why European and Asian sunscreens are more recommended.< /span>

We can see that the left side of the red line in the picture is the United StatesFDAapproved older ingredients, newer unapproved ingredients on the right (the US considers sunscreens to be drugs, so be cautious). Colors The distinction represents the degree of irritation of the ingredients to the skin. Red means very irritating, yellow means irritation to be considered, and green means milder.

This is especially emphasized, benzophenone-3 span>It is recognized by many studies as the most likely ingredient in sunscreens to cause contact dermatitis. It is recommended that you try to avoid choosing sunscreen products that contain this ingredient. Since there are only a few ingredients that can be selected for sunscreen products in the United States, in order to have a higher SPFvalue, choose to use dibenone-3Yes Very common.

In Europe and China, this sunscreen has been avoided as much as possible.< /span>

And then about several other yellow ingredients, such as avobenzone, which itself is very mild to the skin. But the decomposition after decomposition A product that may irritate the skin. Oakleyline is also mild, but studies have shown that when it breaks down, it releases oxygen free radicals, which may also irritate the skin. span>

The problem with ethylhexyl methoxycinnamate is that it is very permeable, and studies have shown that it affects hormones in the body . However, this study is an experiment on animals, and it used a very high dose. Therefore, about the raw material of ethylhexyl methoxycinnamate, governments all over the world consider it safe. There are opinions on the Internet that pregnant women should pay attention Avoid sunscreens containing this ingredient, for fear of affecting the fetus. The root cause is also from this experiment. If you have this concern, you can avoid it, but in fact, this ingredient is very commonly used.

The right side of the picture is relatively mild, and now we use Get more sunscreen. They are gentler on the skin and more stable to light. But none of these are approved in the US. Among them, terephthalmethylene dicamphorsulfonic acid and trozole trisiloxane are patented by L'Oreal. It is also specifically designed to stabilize avobenzone.

Sunscreen products contain other ingredients besides sunscreen.< /p>

Sunscreens (especially chemical ones) contain a lot of oil , the skin feels bad and more greasy. Therefore, in order to adjust the skin feel of the product, other ingredients are added to the product. One of the products I like to add is alcohol (especially Japanese sunscreen products). Friends with oily skin have a better skin barrier and can use alcohol-containing products. If you have dry skin, try to choose an alcohol-free chemical sunscreen. Sensitive skin is best to use pure physical sunscreen. Chemical sunscreens may also be considered if they only contain ingredients in green.

(To be continued...)

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