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When it's summer, products with SPF against UVR, as well as "defenders" from UVA/UVB. But what are these mysterious abbreviations and what meaning does each of them carry? Let's figure it out!

UVR- the simplest of all the abbreviations presented, which means Ultra Violet Radiation - ultraviolet radiation.

IPF- Immune Protection Factor – immunoprotective factor. This is an effective protection of Langerhanz cells and other internal structures of the skin from solar radiation. Scientists are also studying the properties of antioxidants such as green tea, grapes and grape seed oil for their further use as free radical neutralizers.

SPF– the most popular “set of letters” - Sun Protection Factor. Sun protection factor, which indicates the degree of protection against ultraviolet rays. SPF "informs" how many times your normal time in the sun can increase before your skin begins to "burn." The higher the SPF, the greater the protection. The level of protection from UVA is more difficult to determine because they do not cause any sensation of pain or redness. Consequently, in this case, coefficients are applied that determine the so-called pigmentation - durable (PPD) or instant tan (IPD).

UVA- long-wave (320–400 nm) ultraviolet rays of group A, which reach the surface of the earth all year round and even pass through clouds. They make up 95% of all ultraviolet radiation that reaches the Earth. The important thing is that radiation can penetrate window and car glass. Its “strength” does not depend on the time of year or time of day. Reaches the dermis, acting directly on fibroblasts and other skin cells, and, above all, damages collagen fibers. It has also been proven that under the influence of UVA rays it can lead to changes in DNA and the occurrence of mutations. The main consequences of exposure to UVA radiation include skin photoaging and the development of cancer. This is a good reason to remember to use UV filters all year round.

UVB- medium-wave (280–320 nm) ultraviolet rays of group B, which act painlessly, but penetrate the skin so deeply that they reach the dermal cells. They represent 5% of UV radiation reaching the Earth's surface. Its intensity increases from 10 to 15 hours of the day, especially in summer. Does not penetrate window glass or clouds, but easily penetrates water. It is responsible for redness and burns, allergies that occur on the skin after sunbathing, as well as the development of tumors (melanoma).

UVC- ultraviolet rays of group C, which have the shortest waves - 100-280 nm. They do not reach the Earth's surface thanks to the ozone layer.

How to choose the right filter?

In order to protect the skin of infants and small children, it is recommended to use physical filters that are not absorbed into the skin. Chemical filters can cause allergies, irritation or dermatitis. An alternative is cosmetics that contain chemical filters designed specifically for the sensitive skin of children. In addition, all products in this category regularly undergo special tests. For children, products with a minimum SPF 30 filter are recommended in our climate. For infants, the filter should be SPF 50. After sunbathing, be sure to use a moisturizer.

PhototypeI– very fair skin, presence of freckles, red or blond hair, skin easily burns, rarely sunbathes (it is recommended to use creams with SPF of at least 30),

Phototype II– fair skin, few freckles, light hair, skin easily burns, tans with difficulty (SPF at least 20),

Phototype III– dark skin, no freckles, brown hair, skin is quite resistant to burns, tans very easily (SPF 12-15),

Phototype IV– very dark skin, no freckles, dark brown or black hair, skin does not burn, always tans very well (SPF 8-10).

How to properly apply creams with a filter?

• The filter cream is applied to the skin at least 20 minutes before leaving the house;
• Apply the cream every 2.5 hours and renew it after every bathing, sweating and if you have dried yourself with a towel;
• Try not to sunbathe during the day (especially in the first days of summer, when the dose of sunlight is most intense).

Why is ultraviolet radiation dangerous? When and how should you protect your eyes from harmful solar radiation? What lenses with a UV filter can you buy in our online store?

We begin to think about protecting our skin from the sun only with the appearance of its bright summer rays. After all, everyone has heard about the harmful effects of ultraviolet radiation on our health and many are familiar with medical “horror stories”: it causes cancer and wrinkles appear faster. Unfortunately, this is true. However, not only the skin, but also the eyes should be protected from sunlight, since ultraviolet radiation is also very dangerous for them.

By the way, the position: “I see the bright sun - I remember about ultraviolet protection” is not entirely correct. Because there is a type of ultraviolet rays that is active at any time of the year: UVA (spectrum A rays). And yes, even in the harsh Russian winter, when you can’t see the sun at all for 3/4 days, and even on cloudy autumn days.

Tags contact lenses

Ultraviolet rays are electromagnetic radiation in the spectrum between visible and invisible X-ray radiation, the main source of which for people is the Sun. They come in three ranges, determined by wavelength:

• near - UVA
• medium - UVB
• distant - UVC.

Spectrum A and B rays pose a direct threat to people, since C rays do not reach the Earth's surface and are absorbed in the atmosphere. Excess ultraviolet radiation causes burns of varying degrees, cancer, and premature aging of the skin. It is dangerous for the visual organs with such troubles as:

• lacrimation,
• photophobia,
• and in severe cases - corneal burn and retinal damage.

We wrote more about the effects of ultraviolet radiation on vision in.

HOW TO PROTECT YOUR EYES FROM UV rays

To protect your eyes from solar radiation you can and should use:

• sunglasses
• regular (corrective) glasses with specially coated lenses with UV filters (for example, the Crizal brand has these and other lenses with multifunctional coatings)
• contact lenses with UV filters.

Like sunglasses and creams, contact lenses also have several degrees of protection from UV radiation, which are called classes:

• 99% UVB and 90% UVA are blocked first
• The second class filter protects against 95% UVB and 50% UVA.

On packages of contact lenses with a UV filter there is a corresponding mark, usually without indicating the class. If necessary, precise information about the lens protection class can be obtained from the manufacturer.

I would like to note that contact lenses with sun protection are not a complete replacement for sunglasses, but an excellent addition to them. After all, lenses do not protect the area around the eyes, do not save from blinding glare and do not increase the contrast of vision, as, for example, polarized glasses do.

Absolutely all ACUVUE® brand contact lenses from Johnson & Johnson contain UV filters - no other brand can boast such a “breadth” of sun protection across its entire product line. Let's look at a few examples.

Contact lenses 1-DAY ACUVUE® TruEye® - These are soft contact lenses made of silicone hydrogel, a reliable and high-quality modern material. Research results have shown that ACUVUE® TruEye® lenses do not affect the health of your eyes: the condition of your eyes remains exactly the same as before you started wearing the lenses. [I]

They are great for constant wear throughout, even the longest, day. A fruitful work schedule, then playing sports in the gym or jogging in nature, and then planning to drop by for a party with friends? And are you worried whether your lenses will withstand such a rhythm? 1-DAY ACUVUE® TruEye® - will definitely cope with this task! After all, they were specially created for everyone who prefers an active, vibrant and interesting lifestyle.

In addition to the moisturizing component, which will prevent your eyes from experiencing discomfort and a feeling of dryness, ACUVUE® TruEye® lenses have maximum protection against ultraviolet radiation - class 1 filters. Accordingly, they block 99% of UVB rays and block 90% of UVA rays.

The replacement period for these lenses is 1 day. That is, you do not need to worry about storing and cleaning them. At the end of the day you just need to throw them away, and in the morning you will take a new pair out of the package!

Lenses ACUVUE® OASYS® And ACUVUE® OASYS® for ASTIGMATISM Designed for two weeks of wear. The unique technology of these lenses - HYDRACLEAR® PLUS - allows you to forget about dryness and keep the lenses moisturized, which means super-comfortable throughout the day. They are suitable for those who spend a lot of time at the computer, with gadgets and in rooms with dry air (for example, in the office). The excellent oxygen permeability of these lenses allows the eyes to breathe freely. A radiant look and constant comfort - what more could you want from lenses?

Of course, safety! ACUVUE® OASYS® and ACUVUE® OASYS® for ASTIGMATISM have a class 1 UV filter, like ACUVUE® TruEye®, i.e. Blocks over 99% UVB and over 90% UVA .

The advantage of these lenses is that they are more economical in price than daily lenses. However, routine replacement lenses require solutions, storage containers and some time to care for them.

Contact lenses are a medical product that comes into contact with the surface of the eye, and their selection should only be carried out by a specialist - an ophthalmologist or an optometrist. Therefore, although the price can be a very tempting argument in favor of purchasing certain lenses, you still need to focus only on the recommendations of your doctor.

These are beauty lenses for those who do not seek compromises between health and beauty! By highlighting the natural color of your iris with their design, they make your image brighter, your gaze more expressive, and you more confident! However, ACUVUE® DEFINE® lenses should not be confused with colored lenses, because they do not completely change the color of your eyes. There are 2 versions of these lenses on the market: with a brown tint and with a blue tint. The manufacturer states that the lenses are suitable for owners of both light and dark eyes.

In addition to charm and comfort, 1-DAY ACUVUE® DEFINE® contact lenses will also provide you with protection from harmful sun rays, thanks to the presence of a class 1 UV filter. The replacement period is 1 day, which adds points to the convenience and comfort of these lenses.

Contact lenses 1-DAY ACUVUE® MOIST® and 1-DAY ACUVUE® MOIST® for ASTIGMATISM also have sun filters. They block 95% of UVB and more than 50% of UVA rays, because... belong to the 2nd class of protection.

Contact lenses from another manufacturer, BAUSCH + LOMB, are another one-day lenses that will protect your eyes from harmful sun rays - UVA and UVB. They are made of an innovative material - HyperGelTM, combining the advantages of both hydrogel and silicone hydrogel lenses. Excellent oxygen permeability, high moisture content, High DefinitionTM high-definition optics - everything in them is created to make you feel in these lenses as if they are not even there before your eyes! 16 hours of excellent vision and comfort - that's what the manufacturer promises us.

You can choose the right sun contact lenses for you in our Ochkarik optics stores. To avoid waiting, we recommend that you make an appointment with a medical specialist in advance.

When writing this article, materials from the following sites were used: jjvc.ru, acuvue.ru, marieclaire.ru, gismeteo.ru, ru.wikipedia.org, bausch.ru.

[I] D. Ruston, K. Moody, T. Henderson, S. Dunn. Daily contact lenses: silicone hydrogel or hydrogel? Optichen, 07/01/2011. Pages 14-17.

Koch et al. Eyes and contact lenses. 2008;34(2): 100-105. Influence of internal wetting components of contact lenses on higher order aberrations.

Brennan N., Morgan P. CLAE. Oxygen consumption was calculated using the Noel Brennan method. 2009; 32(5): 210-254. Almost 100% of oxygen reaches the cornea when wearing lenses during the day, for comparison: this figure is 100% without lenses on the eyes.

The lenses in Polaroid and INVU glasses are labeled UV-400 or 100% UV-Protection, guaranteeing 100% UV protection. Let's tell you in more detail how it works.

Ultraviolet radiation poses a danger to human eyes: UVA waves are responsible for premature aging of the eyes, UVB can cause irritation of the cornea, UVC are carcinogenic and can damage cell membranes and cause mutations.

The effects of ultraviolet radiation on the eyes are most often cumulative. If you neglect to protect your eyes from harmful radiation for many years, this significantly increases the risk of cataracts and cancer. But there are circumstances in which exposure to ultraviolet light in a matter of days or even hours affects the health of the eyes. For example, many of you have heard about such a disease as “snow blindness” - this is a burn injury to the eye, which often develops in people exposed to ultraviolet radiation reflected from the snow surface - skiers, climbers, polar explorers, winter fishing enthusiasts, etc.

The easiest way to protect your eyes from UV rays is to wear quality sunglasses. But how not to make a mistake when choosing them?

Myths about UV protection glasses:

1. Sunglasses with clear lenses do not protect your eyes.

This is wrong. Untinted glasses can also be excellent eye protection. The fact is that ultraviolet protection is provided by additional coatings or layers in the lens body. And the darkening layer is only responsible for reducing the brightness of the light.

2. D Even non-brand glasses do not protect against ultraviolet radiation.

Let's be honest, numerous professional and amateur tests, publications about which can be found both on the Internet and in various media, have shown that, most often, both Chinese fakes "from the transition" and branded glasses cope equally with ultraviolet protection from official stores.

Does it make sense in this case to buy more expensive sunglasses? This is everyone's personal choice. Obviously, buying items of dubious manufacture is always a risk. Thus, with low-quality sunglasses, there is a risk that their lenses may not have UV protection, or it may be provided by a coating that will quickly wear off during use. In addition, such glasses will be significantly inferior to branded ones in many other respects.

3. Glass lenses protect your eyes better than plastic ones

This really was true, but many decades ago. Thanks to modern technologies, high-quality plastic lenses are not inferior to glass ones in terms of UV protection. Let's say more - modern plastic lenses are much better than glass ones if we evaluate them from the point of view of convenience, durability and safety. Glass lenses are quite heavy in weight and are very easy to break with the slightest impact, and the fragments from them can injure you. Plastic makes it possible to produce the thinnest, almost weightless lenses with various inclusions to protect against ultraviolet radiation, eliminate glare, increase the strength of lenses and protect them from scratches.

Read the label: UV-400

A proven brand and the inscription on the label “UV-400” guarantee 100% eye protection from ultraviolet radiation. You can also find the spelling 100% UV-Protection or 100% UV protection. This means that the lenses provide eye protection from all ultraviolet radiation with a wavelength of less than 400 nm - that is, from UVA, UVB and UVС rays.

There is also a standard "UV-380" - the presence of this marking means that the lenses block light waves with a length of less than 380 nm. According to most experts, glasses labeled UV-380 provide only 90% eye protection from harmful influences, and only a few experts are inclined to claim that this degree of protection is sufficient for eye health.

Visible radiation - electromagnetic waves perceived by the human eye, are approximately in the wavelength range from 380 (violet) to 780 nm (red). What is to the right of the visible spectrum, i.e. with a wavelength of more than 780 nm is infrared (IR) radiation, invisible to humans. To the left, i.e. with a wavelength from 250 to 400 nm, there is that part of the spectrum invisible to humans that interests us today - ultraviolet (UV). Exposure to ultraviolet radiation (UV) affects the eyes, skin and immunity. In ordinary life, direct sunlight does not reach the eyes, especially when the sun is at its zenith, but due to reflections from surfaces, it is estimated that 10-30% of the radiation (depending on external conditions) that reaches the earth's surface ends up in the eyes. In the case of paragliders, when pilots have to raise their heads towards the sun, direct rays also hit them. For winter sports (skis, snowboarding, kite, etc.), as well as for water activities (kite, surfing, beaching, etc.), the amount of reflected radiation entering the eye is greater than average.

Based on wavelength, UV radiation is divided into 3 components: UVA, UVB and UVC. The shorter the wavelength, the more dangerous the radiation. UVC, the shortest wavelength and most dangerous range of ultraviolet radiation, fortunately does not reach the earth's surface thanks to the ozone layer. UVB – radiation in the range of 280-315 nm. Approximately 90% of UVB is absorbed by ozone, as well as water vapor, oxygen and carbon dioxide as sunlight passes through the atmosphere before reaching the earth's surface. UVB in small doses causes a tan, in large doses it burns and increases the chances of skin cancer. Excessive exposure of the eyes to UVB rays causes photokeratitis (sunburn of the cornea and conjunctiva, which can lead to temporary loss of vision (severe photokeratitis is often called “snow blindness”). The risk of photokeratitis increases at high altitudes, as well as in snow, if you do not protect your eyes from ultraviolet radiation. Note that the impact of ultraviolet radiation in the UVB range is limited to the surface of the eye; these ultraviolet rays practically do not penetrate into the eye.

Ultraviolet radiation in the UVA range (315-400 nm) is close to the visible spectrum, and in the same doses is less dangerous than UVB radiation. But these ultraviolet rays, unlike UVB, penetrate deeper into the eye, damaging the lens and retina. Exposure of the eyes to UVA over the long term increases the risk of a number of dangerous eye diseases, including cataracts and macular degeneration, which is considered the leading cause of blindness in old age. Well, let’s mention the part of the visible spectrum corresponding to the blue rays of the visible spectrum, about 400 -450 nm, (HEV “high-energy visible light”), which are directly adjacent to the long-wave part of the UV range. Long-term exposure to these high-energy visible rays is also thought to be harmful to the eyes because they penetrate deep into the eye and affect the retina.

The damaging effect of ultraviolet rays on the eyes depends on a number of factors:

• Duration of stay outdoors
• Geographic latitude of the location. The most dangerous zone is the equatorial zone
• Altitude. The higher, the more dangerous
• Time of day. The most dangerous time is from 10-11 a.m. to 2-4 p.m.
• Large surfaces of water and snow that highly reflect the sun's rays

Thus, constant exposure to ultraviolet radiation on the eyes has a harmful effect on the surface of the eye and its internal structures. Moreover, the negative effects have the ability to accumulate: the longer the eyes are exposed to the damaging effects of ultraviolet radiation, the higher the risk of developing pathologies of the eye structures and age-related diseases of the organ of vision.

Sunglasses are one way to limit the amount of harmful radiation reaching your eyes. Since the doses of ultraviolet radiation received over a lifetime accumulate, increasing the risk of eye diseases, it is recommended to regularly wear sunglasses outdoors.

Measurements and results

Lens characteristics and concepts that we will need when analyzing tests and measurements: Optical density. This is the decimal logarithm of the ratio of the intensity of the incident radiation to the transmitted radiation. D=lg⁡(Ii/Io) That is if the optical density of the lens is 2, then it reduces the radiation intensity by 100 times, blocking 99% of the incident radiation. If D=3, then the lens blocks 99.9% of the radiation. In addition, sunglasses lenses are divided by transparency (for the visible spectrum):

• Transparent F0, 100 - 80% light transmission used in twilight or at night, sports and safety glasses against snow and wind;
• Light F1, 80 - 43% light transmission, glasses for cloudy weather;
• Medium F2, 43 - 18% light transmission, used in partly cloudy weather;
• Strong F3, 18 - 8% light transmittance, for protection from bright daylight;
• Maximum strength F4, 8 - 3% light transmission, for maximum protection in high altitude conditions, at ski resorts, in the snowy Arctic in summer. Not intended for driving a car.

For measurements we have a spectrophotometer:

We selected several glasses and lenses from different manufacturers at completely different prices. The cost of glasses ranged from 1 to 160 Euros (70 -11,000 rubles). So, let's start from expensive to cheap: The first 2 lenses are GloryFy, brown F2 and gray F4. Glasses of this brand with such lenses cost approximately 11,000 rubles.

Transmission graph in %, i.e. what percentage is the intensity of the transmitted radiation from the incident one:

Red shows the transmission of the brown F2 lens, and blue shows the transmission of the gray F4 lens. As can be seen from the graphs, both lenses cut all ultraviolet light well. In addition, it is clear that the brown F2 lens cuts the blue part of the spectrum much better, the gray F4 is essentially neutral (i.e. does not distort colors) and, being darker (F4 versus F2 for the brown one), darkens more strongly throughout the entire spectrum. For a more accurate assessment of how well ultraviolet radiation is blocked, here is a graph of the optical density for these lenses:

the red line is for the brown lens F2, and the blue line is for the gray lens F4

It can be seen that the optical density is greater than 2.5 over the entire ultraviolet range, i.e. More than 99% of ultraviolet light incident on the lens is blocked. To clarify, I will give the values ​​for these lenses for a wavelength of 400 nm. Optical density for gray F4 D=3.2, for brown F2 D=3.4. Or the transmittance from the incident radiation for gray F4 is 0.06%, and for brown F2 it is 0.04%.

Let's move on. Here we present graphs of transmittance and optical density for glasses of an average price category: Smith and Tifosi - both lenses are gray, dark. The cost of glasses is about 4000-6000 rubles. And cheap glasses costing about 700 rubles - 3M and Finney - both lenses are also neutral, i.e. gray, dark. For starters, the transparency for all these mentioned lenses

From the graphs it can be seen that all lenses are category F3. In addition, it is noticeable that the lenses of cheap glasses (3M and Finney) are worse at cutting near ultraviolet light, UVA in the range of 385-400 nm. Now for all these 4 points we give the transmittance value at a wavelength of 400 nm:

• Smith T=0.002%
• Tifosi T=0.012%
• Finney T=5.4%
• 3M T=9.4% and optical density at the same wavelength:
• Smith D=4.8
• Tifosi D=3.9
• Finney D=1.26
• 3M D=1.02

It is clearly visible that cheap 3M and Finney glasses do not meet the UV400 protection requirements. They begin to protect normally from wavelengths of 385 nm and below.

But we have the cheapest glasses, unbranded (Auchan glasses). Cost 70 rubles or 1 euro. The lens is yellow, the transmission looks like F1 category. Transparency:

Optical Density:

For a wavelength of 400 nm, the transmittance was 0.24% and the optical density was 2.62. This lens meets the UV400 requirement.

Conclusions:

It is clear that cheap glasses do not have a stable quality of protection: 2 out of 3 samples were not satisfactory. Branded glasses of the upper and middle price categories did a good job of protecting against ultraviolet radiation. In addition, when we talk about protection from ultraviolet radiation with glasses, we should take into account that light can also penetrate from the side of the frame, so, of course, glasses that cover the entire field of view and do not allow light to enter the eyes past the lenses of the glasses are better protected. And of course, when choosing glasses, you should consider how comfortable they sit on your face, because you have to wear them for hours. For people involved in active sports and frequent travelers, it is important how durable the glasses are: it’s unpleasant to find fragments in your backpack at the right time instead of glasses.

Despite the fact that the world has been using sunscreens for several decades, many people still interpret the numbers on sunscreen packages in their own way. What SPF and PA values ​​will definitely protect you from the sun? And do you know how to use sunscreen correctly?

Products with UV filters have different compositions and different principles of action. According to the principle of action, they can be divided into physical (reflecting) and chemical (absorbing).

Very small particles are applied to the skin, which reflect the sun's rays. Such products use two active ingredients - titanium dioxide and zinc oxide, while the remaining active sunscreen substances can be classified as chemical. Physical sunscreens reflect UVA and UVB rays and can also reflect infrared radiation. They cause almost no irritation and are suitable even for delicate infant and child skin.

The downside is that the higher the content of active ingredients (and, accordingly, the higher the SPF factor), the greater the discomfort from their use: white marks on the skin, clogged pores, a sticky feeling. With a small content of active ingredients (SPF below 30), the feeling of use is more comfortable, but the protection against UVA rays (PA+, PA++) is insufficient.

Of the two filters mentioned above: titanium dioxide and zinc oxide, zinc oxide protects against UVA and UVB radiation. Titanium dioxide is more effective in protecting against short-wave UVA and UVB rays. Thus, when buying physical sunscreens, it is better to choose a product that contains both or only zinc oxide, but not one that contains only titanium dioxide.

Chemical principle of operation of a UV filter (absorbing)

Filters of this operating principle absorb UV radiation and annihilate it, converting it into energy that is safe for the skin. Chemical UV filters include cinnamate, octocrylene, butylmethoxydibenzoylmethane (avobenzone), benzophenone-2 (oxybenzone) and others.

They have many advantages: they leave a feeling of lightness and freshness on the skin after use, have a variety of release forms (for example, gel), but effectively protect only from UVA rays, and even products with a low SPF factor cope well with this function (below 20).

The disadvantage of these active ingredients is that each of them blocks only part of the radiation, and when used separately they are not very light-stable. Therefore, it is necessary to use products containing several types of chemical filters. Also, products with chemical filters can cause burning, itching of the skin, and eye irritation.

The best sunscreens. What to choose?

There is a lot written on the Internet that chemical products are harmful to the skin because they contain carcinogenic components, and therefore it is worth choosing sunscreens with physical filters. Such statements have no scientific confirmation and are based on rumors. Both physical and chemical filters have strengths and weaknesses.

There are three types of sunscreens on sale: only with physical filters, only with chemical filters, and mixed ones. The latter are the most common, as they have all the advantages of their components and at the same time compensate for their disadvantages. Such products are the right choice for those who are not used to using sunscreen.

Creams with UV filters not only save you from sunburn, they also protect your skin from aging and cancer. It is very important when purchasing a sunscreen to make sure that it provides good protection against both UVA and UVB rays. The surest way to know the effectiveness of a sun cream is to read its ingredients. For the convenience of consumers, two indicators are used (SPF and PA), which indicate the degree of protection of a particular product. But many still do not know what these indicators mean.

What is SPF (Sun Protection Factor)?

This is an indicator of the degree of protection against UVB rays. These rays are especially strong in summer and can cause burns and redness of the skin. Previously, you could find products with SPF 60 and even 100 on sale, but recently in Korea, if the SPF value exceeds 50, they simply put the mark 50+ (a similar situation is in Russia).

For unknown reasons, many people believe that these numbers indicate how long the sunscreen will last after application. This is, of course, not true; It is correct to perceive SPF as a quantitative indicator of the degree of protection against UVB rays.

SPF is a quantitative measure of UV blocking
SPF 15 = 14/15 = 93% UV blocking. Penetration of rays into the skin is 1/15 (7%).
SPF 30 = 29/30 = 97% UV blocking. Penetration of rays into the skin is 1/30 (3%).
SPF 50 = 49/50 = 98% UV blocking. Penetration of rays into the skin is 1/50 (2%).
SPF 90 = 89/90 = 98.8% UV blocking. Penetration of rays into the skin is 1/90 (1.2%).

We see that SPF 15's ray blocking ability is a whopping 5% lower than SPF 50's, while the difference between SPF 50 and SPF 90 is not that great at just 0.8%. After SPF 50, the ability to block sun rays practically does not increase, and buyers often think that SPF 100 is twice as powerful as SPF 50. To avoid such mistakes, in Asian countries, as well as in the United States, everything above 50 units has become mark as SPF 50+. This stopped the senseless race of numerical indicators between products with SPF above 50.

What is PA (Protection Grade of UVA)?

The PA index is used in Asian countries, primarily Korea and Japan, as an indicator of the degree of UVA protection. This indicator is higher the more “+” signs there are after the letters “PA”. UVA radiation is approximately 20 times stronger than UVB radiation and, penetrating deeply into the skin, can lead to the appearance of wrinkles, age spots and freckles.

To understand what the PA indicator is, you need to have an idea of ​​PPD (Persistent Pigment Darkening). This index is used in Europe (primarily France) to indicate the degree of UVA protection. PPD has a numerical value, and the higher it is, the stronger the protection. We can say that PA+, PA++, PA+++ are modified PPD indicators (weak, medium, strong).

PA+ corresponds to PPD 2–4.
PA++ corresponds to PPD 4–8.
PA+++ corresponds to PPD 8–16 (in Korea, PA+++ is the maximum degree of protection).
PA++++ corresponds to PPD 16–32 (used in Japan since 2013).

How effective is my sunscreen against UVA rays?

According to European standards, in order for a product to effectively protect against both types of UV rays, the PPD value must be at least a third of the SPF value. That is, if SPF 30, then PPD must be at least 10 (PA+++), and if SPF 50+, then PPD must exceed 16 (PA++++).

You can also check the composition and quantity of substances contained in the product. On American products, the manufacturer is required to indicate the amount of active ingredients, which include UV filters. One of the most effective UV filters is avobenzone with its content in the composition of at least 3%, and if in addition to it the photostable elements octocrylene and oxybenzone are also indicated in the composition, you can be sure that this product is an effective means of protection against UVA radiation.

What rules must be followed to ensure that your sunscreen works perfectly?

To check the degree of SPF protection, you need to apply the product to the skin at the rate of 2 mg per 1 cm2 and expose this area of ​​the skin to the sun's rays. The required degree of protection is determined by whether redness appears on the skin after such a test.

However, in general, buyers do not use even a third of the required volume. Approximately 0.8 g of product should be applied to the face; this corresponds in volume to the amount that will fill the depression in the center of a cupped palm.

If you apply more than the required amount, you can increase its original SPF value. But keep in mind that if you apply half the required volume of a product with an SPF index of 50 units, then its effectiveness will not drop to 25 units, as it might seem, but to 7.

Apply sunscreen 30 minutes before going out

This is necessary so that it has time to be absorbed into the skin, and is necessary not only for chemical filters, but also for physical ones. After applying a product with physical filters, the skin first becomes oily or slippery, and it is better not to leave the house until it becomes matte.

Renew the product every 2-3 hours

All sunscreens available today, whether they are SPF 30 or 50, need to be reapplied every 2-3 hours in order for them to continue to work effectively at their SPF rating. The fact is that the components of these products gradually disintegrate under the influence of secretions of the sebaceous and sweat glands, as well as ultraviolet radiation.

Renew your sunscreen after swimming

If you get any part of your body wet, dry it and reapply sunscreen. Even if your sunscreen is considered water-resistant, it's still a good idea to reapply it after swimming.

And if you're sweating profusely, dry your body with a towel and reapply sunscreen. If you apply the product to wet skin, it will be diluted in water and will not work properly, so only use it on dry skin.

Avoid exposure to the sun

UV radiation is strongest in the summer between 10am and 3pm. If you must go outside during this time, reapply sunscreen before going out. Don’t be frivolous, don’t think that “nothing will happen if you jump outside for a short time, for 10 minutes.” The harmful effects of sun rays on the skin have a cumulative effect and cause photoaging. We spend huge amounts of money on brightening and anti-aging serums, but the effect of using them can easily be ruined by spending just 10 minutes in the sun.

Don't Rely on Sunscreens Alone

Applying the right amount of sunscreen regularly, every 2-3 hours, is more difficult than it may seem. To ensure your sunscreen works properly, use sunscreen aids such as a wide-brimmed hat and sunglasses, which can act as UV filters in themselves.

In the summer at sea you can see people who do not apply sunscreen to their bodies, but instead wear thin T-shirts or sweaters, but thin fabrics have a UV protection level of only 5–7 units. Thus, they offer almost no protection from UVA radiation, which leads to skin aging. In addition, clothing that gets wet in water loses most of its protective function, up to 2-3 units.