All about SPF – part 2 “Factors, duration of action. Which SPF is best to choose and how to use it?”

Before we explain how SPF is calculated, it is important to note that testing for SPF factor definitions has limitations, as it does not always apply to real-life situations, since tests are conducted on the skin of specific individuals, the conditions are controlled, and the intensity of ultraviolet radiation is fixed. In real life (as explained above), the intensity of UVB rays varies, while the intensity of UVA rays remains constant. The changing intensity of UVB rays affects how long it takes for the skin to redden (burn) without the use of sunscreen.

% protection from UVB rays, depending on the level of protection factor (based on regulated tests):

SPF15 protects the skin from 93% of rays

SPF30 blocks almost 97%

SPF50 blocks 98%

Looks practically the same, doesn’t it?

However, looking at it from another angle:

SPF30 lets through about 3% (1/30th) of UVB rays

SPF50 lets through only about 2% (1/50th)

Thus, SPF30 protection lets through 1.5 times more rays than SPF50 protection.

For daily use, cosmetic products with SPF30 protection are an excellent solution. But if you know that your skin will be exposed to intense midday sun, you might want to use a higher SPF factor along with other protective measures, such as hats and long-sleeved clothing and additional protection from ultraviolet rays.

HOW LONG DOES SPF15, 30, 50 LAST?

It was previously thought that simple math was enough: if you know that your skin turns pink or just starts to darken within 10 minutes of being in the sun without sunscreen, then SPF15 will provide you with 150 minutes of protection (10*15), SPF30 – 300 minutes, and so on.

The math above is how researchers explained SPF factors to people, but this simplification is a drawback of the overall descriptive system of how SPF works. The SPF factor is not just the amount of time the skin is exposed to ultraviolet; rather, it is the time and amount of exposure, that is, the intensity of ultraviolet radiation depending on your location in the world and other factors such as cloud cover, latitude, time of year, and proximity to reflective surfaces like water and sand.

In summary, it can be said that the intensity of solar energy emitted by the sun affects how much of it your skin receives. For example:

1 hour at 9:00 AM is not the same as 1 hour at 1:30 PM. At 1:30 PM, it is already 15 minutes of sun exposure.

Or – 1 hour at 9 AM is the same as 1 minute at 1 PM at high altitude with reflective snow.

– each of the above time intervals can deliver the same intensity of UV radiation to the skin, despite radically different timestamps.

Therefore, sunscreen that is sufficient for one hour of protection at 9 AM will only work for 15 minutes at lunchtime (1:30 PM).

The same goes for weather conditions: it is clear that in cloudy weather, SPF20 is sufficient for a walk in the city, but for the same walk in the blazing sun, you need a product with a maximum SPF50 protection factor.

HOW AND WHEN TO APPLY?

At the microscopic level, the skin is a series of peaks and valleys. Applying sunscreen about 20 minutes before going out in the sun allows the product to get into the valleys and properly bond with the skin.

Many sunscreens recommend applying every two hours. But looking at it from another perspective, it’s like painting your house. The first coat provides acceptable coverage, but reapplying after 20-30 minutes in the sun – after the first coat has “dried” – will give much more reliable coverage. And this will cover areas that you may have missed or covered too thinly during the first pass.

In general, the Japanese recommend applying sunscreen twice, and if you cannot wait those 20 minutes, then apply the second layer immediately as the first one absorbs. From my own experience, it is definitely better to apply SPF twice on problematic areas of the skin, with increased pigmentation or unevenness, typically on the prominent areas of the face – cheekbones, nose, and forehead.

How much to apply in grams?

Additionally, it should be used in a sufficiently generous layer. Most people use too little (from a quarter to three-quarters) of the amount of sunscreen needed to achieve the sun protection claimed on the label. A teaspoon per hand/leg is a good rule. Add half a teaspoon for the face and neck, and a spoonful for the chest, back, and abdomen. In total, it will be about 8 teaspoons (~16ml) if you are at the beach in shorts or a bikini.

Apply sunscreen every two hours or more frequently if you are active (sweating, towel-drying, engaging in physical contact with anything that may rub it off), even if the bottle says it will last for 4 hours. It is also advisable to check the expiration date of your cream.

HOW LONG CAN I STAY IN THE SUN WITH SUNSCREEN?

It is reasonable to stay in the sun no longer than necessary to complete your planned activities. Staying in the sun longer just because you have a sunscreen “armor” (which it is not) is a bad idea.

Is there still a chance of getting sunburned if you apply sunscreen correctly? No. If sunscreen is applied correctly, it performs its function of reducing ultraviolet radiation exposure, preventing the biological process of tanning.

The degree of protection from UVA is indicated on the packaging as a designation: PA

• – PA+++ – maximum protection
• – PA++ – medium protection
• – PA+ – minimum protection

WHAT SPF DO I NEED?

The choice of a product with an SPF factor depends on how long it takes for your skin to change color (from pink to red or show signs of tanning) under the influence of ultraviolet rays without sun protection. Once you determine this time – and you may have to estimate it – multiply that number by the SPF factor to get a baseline time during which the sunscreen you choose will protect you under normal conditions.

“Normal conditions” refer to the amount and intensity of ultraviolet radiation that typically affects your skin. If you know that your skin will be subjected to more intense and/or prolonged ultraviolet exposure, you need to choose a sunscreen with a higher SPF factor and apply it more frequently. All UV filters break down and become less effective with constant exposure to sunlight. Reapplying the cream at regular intervals will provide the best sun protection.

In fact, regular use of broad-spectrum sunscreen (against both UVA and UVB) (reminding you that on Japanese bottles this is indicated by the PA labeling with the subsequent number of “+” signs), as shown, reduces the risk of developing non-melanoma skin cancer and melanoma, the most aggressive form of skin cancer, says Dr. Nana Duffy, MD, FAAD.

But when choosing a sunscreen, you will have to decide for yourself:

what you will apply – a sunscreen with physical or chemical sun filter. And does it even matter which one you use? The answer is definitely – no.

Despite the common belief that physical filters work as a shield, reflecting ultraviolet rays, while chemical ones absorb them – this is a misconception. Both chemical and physical filters work as ultraviolet absorbers. Physical filters reflect only 5% of rays, while the rest are absorbed.https://onlinelibrary.wiley.com/doi/10.1111/phpp.12214

It is believed that products with physical filters are more suitable for skin prone to reactions and rosacea, as the risk of reaction to the sunscreen filter is lower and the degree of tissue heating is also lower (which is safer for skin with closely located vessels).

Both types have their pros and cons, which we will discuss in the next part of the article series dedicated to SPF.

DIREIA Stem Protect UV Cream day cream with sun protection SPF50+/PA++++

The composition of Steam Protect UV Cream includes sunscreen filters: titanium dioxide, ethylhexyl methoxycinnamate, ethylhexyl triazone.

DIREIA Stem UV Cream – sunscreen with human adipose stem cell extract providing maximum protection for the skin against UVA and UVB rays. The composition includes a combination of chemical and physical filters

SPF50+/PA++++

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NABOCUL Sunmure UV Block sunscreen emulsion SPF32 PA +++

The composition of NABOCUL Sunmure UV Block is based on a physical filter – titanium dioxide

Water-resistant emulsion Sunmure with sun protection SPF32 / PA +++. The emulsion blocks the harmful effects of ultraviolet rays, thereby preventing the appearance of pigmentation spots and freckles caused by the sun.

The sunscreen is easy to apply and spread on the skin, absorbs quickly, and does not leave a sticky feeling. Immediately after application, it slightly whitens, but after 10 minutes it “settles” and becomes completely invisible. Suitable as a makeup base.

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PLAMINE UV Perfect Lotion SPF50 PA++++ moisturizing sunscreen lotion antioxidant

The composition of Plamine UV Perfect Lotion includes physical sunscreen filters:

zinc oxide, titanium dioxide, and silica

Sunscreen lotion-fluid with physical filters with maximum protection factor SPF50 PA++++. The lotion effectively protects the facial skin from ultraviolet rays, photoaging, and prevents dryness.

The sunscreen lotion contains fullerene – a powerful antioxidant, which reduces damage caused by ultraviolet rays and prolongs skin youth, alleviates inflammation, and gives the skin a beautiful healthy color.

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In the next part of the articles about the Sun and Man: What is the difference between Physical (mineral) Filters and Chemical;
We will analyze the components of Sunscreens, which of them are safer for humans and the environment, and which are less so.
The article will present a complete data table on Sunscreens from the website – so no customer will have questions and making a decision in choosing an SPF product will be clear and easy from now on!

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