Sunscreen: 11 Questions We All Ask
What does SPF mean?
SPF stands for Sun Protection Factor, the index that measures how well a sunscreen protects skin from UVB rays.
The SPF number indicates how much UVB radiation the product filters out. SPF 15 filters out about 93% of UVB rays, SPF 30 97%, SPF 50 98%. So what, practically, is the difference between SPF 30 and 50? In percentage terms it seems small, but with SPF 30 about 3% of UVB rays get through, and with SPF 50 2%. Over long exposure, that one percentage point translates into significantly higher protection.
SPF 10 and 20 are no longer recommended as the first line of protection: they filter out too little UVB, especially considering that in real life people tend to apply less sunscreen than they should. The starting recommendation today is SPF 30 minimum.
And SPF 100? In Europe, the highest value that can be declared on the label is "50+": protection is above 98%, but the exact number is not written because beyond that level the differences are too small. No sunscreen, in any case, blocks 100% of UV rays. If you see a sunscreen with SPF 100, it's probably an American product, where that wording is allowed.
UVA and UVB rays: what's the difference?
UVB and UVA are two types of solar radiation that behave differently and cause different kinds of damage.
UVB rays have a shorter wavelength and stop at the surface layers of the skin. They are the main cause of redness and sunburn: the acute damage, the kind you see after an afternoon at the beach. When you read an SPF value on a label, it refers to protection against them.
UVA rays have a longer wavelength and go deeper, all the way to the dermis. They are the radiation linked to photoaging: wrinkles, spots, loss of elasticity. Unlike UVB, they pass through glass and clouds. That's why sunscreen makes sense in winter too, in the car too, and behind an office window too.
On the label, SPF alone is not enough to say that a product protects against both types of radiation. To be sure a sunscreen also covers UVA, look for the circled UVA symbol, meaning the word "UVA" inside a circle. If it's not there, the company has not carried out the specific UVA tests.
"It's the first check to make when choosing a sunscreen," says Dr. Maria Pia Priore, pharmacist, cosmetologist, and founder of Skin First. "More than the SPF number".
Can you tan with sunscreen?
Yes, but less and more slowly.
Tan is not a positive effect of the sun on the skin: it's a sign of damage. UV rays damage the DNA of skin cells, and the skin responds by activating melanocytes to produce melanin, the pigment that gives the skin a darker color as a defense against the radiation that keeps coming. By the time we tan, the cellular damage has already happened.
No sunscreen blocks 100% of UV rays. SPF 50 filters out about 98%: that remaining 2% can still trigger melanin production, especially with long exposure. That means that with SPF 50 sunscreen you still tan, just more slowly and with much lower cumulative damage.
The goal of sunscreen is not to never tan. It's to protect against acute damage, such as redness, and chronic damage, such as photoaging and spots.
How long does sunscreen last?
When does sunscreen expire? On sunscreens, the expiry is indicated by the open-jar symbol, the PAO (Period After Opening): the number beside it shows how many months the product should be used within after opening, from 6M to 24M. For most sunscreens the value is 12M.
Actual shelf life also depends on storage. Sunscreen filters are molecules that degrade with heat, direct sun exposure, and temperature changes. A sunscreen left in a car in the sun, or in a bag under a beach umbrella all summer, can lose some effectiveness even before its stated expiry date.
Practical signs of a sunscreen that's gone off: separation in the bottle, a change in texture, an altered smell. If you notice any of these, it's best to replace it. At the start of summer, checking a sunscreen left over from the previous year is a sensible habit.
When should sunscreen be applied?
A few minutes before exposure. There's a practical reason: once applied, the product needs a little time to spread evenly and bond with the skin. Applying it at the exact moment you step outside means risking some of the sunscreen being rubbed off immediately by clothing, sweat, or a towel before it has done its job.
There's good news for people who use sunscreen every day: if it's the last step in the morning skincare routine, the necessary time has already passed by definition. Apply it after face cream, get dressed, and by the time you leave home the sunscreen is ready to do its job.
When should sunscreen be reapplied?
It depends on how you spend your day.
In the city, in the office, or in the car, the morning application, done as the last skincare step, may be enough if exposure to light is limited. If, however, you stay outdoors for a long time or are exposed to light (even while driving or near windows), it's recommended to reapply during the day.
If you're in the sun, at the beach, in the pool, on a walk, at a stadium, the rule changes: sunscreen should be reapplied every two hours, and every time after swimming or heavy sweating. Two hours is not a symbolic threshold: it's the average time it takes for the protective film to thin due to sebum, sweat, towels, and rubbing.
If you're already wearing makeup, you can reapply sunscreen over makeup too: put some product on the back of your hand, soak a sponge, and pat it onto the face without rubbing, repeating until the area is covered.
At which step of your skincare routine should sunscreen be applied?
It's the last step of the morning skincare routine, before makeup.
The correct order in the morning is: cleansing, any serum or booster, eye cream, face cream, and sunscreen last. Never before face cream, and never mixed with other creams in the palm of your hand: diluting it reduces the protection stated on the label. The right gap between face cream and sunscreen is simply the time needed for the cream to absorb, a few minutes.
Our SPF 30 and SPF 50 Face Fluids are designed for exactly this step: the last step of your daily skincare routine, every morning of the year. The fluid, lightweight texture layers easily over face cream and under makeup, without weighing skin down or leaving residue.
One note: sunscreen is applied only in the morning. In the evening it doesn't make sense, and creams with SPF shouldn't be used as night cream.
How much sunscreen should you apply to your face?
Generously. Most people apply too little, and that's one of the main reasons sunscreen sometimes doesn't protect as it should.
The ideal amount depends entirely on the size of the area being covered, and each area has its own needs (e.g. the face). The practical benchmark for making sure you apply enough is simple: spread a visible, even, generous layer over the skin. And don't forget the areas that are often overlooked: neck, ears, temples, hairline, backs of the hands. These areas are exposed just as much as the face, but rarely covered.
Sunscreen even when it's cloudy?
Yes. Why should you put on sunscreen when it's cloudy? The answer lies in UVA.
Clouds block UVB rays to a large extent, but on an overcast day up to 90% of ultraviolet rays can still reach the skin, especially UVA. And UVA rays are the ones responsible for photoaging: wrinkles, loss of elasticity, and the appearance of spots over time. They are the silent damage, the kind you don't see the next day like a sunburn, but that builds up over the years.
There is a more reliable indicator than the weather for knowing when protection is needed, and that's the UV Index: it measures the intensity of UV radiation on a scale from 1 to 11+. The higher the value, the more intense the radiation. It changes depending on date, season, location, actual cloud cover, and altitude. The practical rule: with a UV Index of 3 or higher, sunscreen is recommended. You can check it in all major weather apps, or by searching "UV Index" together with your city name on Google.
Mineral or chemical filters: which should you choose?
There is no right or wrong choice: both protect, both are safe, and both are regulated by the same European authorities.
The marketing around mineral filters has over the years encouraged a series of labels that don't reflect the reality of the formula. Mineral filters are not "natural" or "chemical-free": zinc oxide and titanium dioxide, the only two allowed under the European Cosmetic Regulation, are largely obtained through industrial synthesis and chemically coated to fit into formulas.
Mineral (or "physical") filters are often described as a screen that reflects UV rays, but in reality they work like chemical ones: most of the protective action happens through absorption, not reflection.
The concrete differences concern the cosmetic finish. Mineral filters tend to leave a white cast on the skin that rarely disappears completely, and they layer less well under makeup. Next-generation chemical filters are photostable, have lighter textures, and fit better into daily skincare.
Our SPF 30 and SPF 50 Face Fluids are formulated with broad-spectrum, photostable, next-generation chemical filters, in line with a product designed for daily use under makeup and quick absorption.
In the end, the best sunscreen is the one you actually apply, every day.
Sunscreen cream vs. sunscreen milk: what's the difference?
The difference is in the format and texture, not in effectiveness.
A sunscreen cream or fluid has a more structured consistency, is applied with the fingers, and is designed for smaller areas where precision matters: face, neck, décolleté, hands. A sunscreen milk, on the other hand, has a more fluid texture, often in spray format, and is designed to cover large areas quickly, such as the body, on holiday or at the beach.
With the same SPF, applied in the correct amount, they protect equally well. The choice depends on how you use it: a fluid or cream is more practical for the face, where protection is layered with other products and makeup; a spray milk is more functional for the body during active sun exposure.
Skin First SPF 30 and SPF 50 Face Fluids are made for the face and for daily use: 50 ml in a format designed to last a long time with one application a day, and to fit into everyday skincare as the final step.
Sunscreen is the skincare product with the highest prevention payoff of all. The sun is the main cause of photoaging, more than any anti-wrinkle cream can make up for over time. And yet it remains the most underestimated product. I often hear people say, "I only put it on when I go to the beach." But even one application in the morning, every day, makes a difference you can see in ten years.
— Dr. Maria Pia Priore, pharmacist, cosmetologist, and founder of Skin First®
In conclusion
Sunscreen has been talked about for decades, yet it remains the product surrounded by the most doubts and half-truths. Most of them are solved by a change in perspective: sunscreen is not "that thing you put on at the beach." It's the first skincare step you do in the morning, every day, in any season. How to choose the right sunscreen, how much to use, when to apply it — these are questions that become clear once sunscreen becomes part of your morning routine.
The sun doesn't wait for skin to be ready. It's up to us to be ready first.
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