If you've ever wondered what makes a sunscreen effective, then this article is for you.
First, you need to understand how sunscreens work. Topical sunscreens absorb or scatter ultraviolet (UV) radiation. Sunscreens first emerged in 1928 and have since become a staple for skin cancer prevention, and also for fighting the general damage sun exposure can cause to your skin.
A 4.5-year study in Queensland, Australia, with 1,600 individuals, found that the use of sun protection factor (SPF) 16 broad-spectrum sunscreen decreased the incidence of squamous cell carcinoma by 38%.
The most important protection provided by sunscreen is known as SPF. What many users don't know is that SPF is mostly relevant for sunburn protection and not other biological factors, which is why you should pay attention to things like immune protection factor (IPF).
What is IPF, and does it matter?
The immune protection factor measures something SPF entirely ignores, which is your sunscreen's ability to prevent UV-induced suppression of your skin's immune response.
UV radiation burns the surface of your skin while also actively suppressing the local immune system, reducing your skin's ability to detect and destroy abnormal cells before they develop into skin cancer.
A sunscreen with a high IPF rating maintains your skin's immune surveillance function even during prolonged sun exposure, providing a layer of protection that SPF ratings were never designed to capture.
What is SPF, and does it matter?
SPF basically means how much longer skin covered with sunscreen takes to burn compared with unprotected skin.
A study by Diffey BL. found that the amount of sunscreen applied, how it is spread, and the UV-absorbing properties of the sunscreen are all important. However, most important of all is the level of compliance on the part of the user. This means how much sunscreen is applied and how well it is applied.
Amazingly, how well the sunscreen absorbs UV contributes only about 10%! What this means is the more you're motivated to use your sunscreen frequently, the higher the importance of the actual SPF number.
This is one of the main reasons I love Korean sunscreens.
The health benefits and better texture mean you'll actually enjoy using it.
Also, it's important to know that higher SPF levels mean the water content decreases as the concentration of UV filters increases to deliver the higher protection.
This means the sunscreen is more difficult to spread, and you'll usually apply a smaller amount than you would with a lower SPF product.
How do Korean sunscreens solve this problem?
The answer is cosmetic elegance.
Cosmetic elegance is when you love the way a sunscreen feels, spreads, and absorbs on your skin.
When a sunscreen feels heavy, greasy, or leaves a white cast, you apply it less and skip reapplication, which means your skin doesn't get the protection it needs.
Korean sunscreens achieve cosmetic elegance through two parallel developments that Western brands have largely been unable to replicate.
The first is access to next-generation UV filter chemistry and formulation philosophy that treats sunscreen as skincare rather than a separate protective coating.
Why you'll love Sunscreen-as-Skincare
The more interesting distinction between Korean and Western sunscreen formulation comes down to a fundamentally different answer to the question of what a sunscreen is supposed to do.
Western sunscreen development has historically been driven by maximising UV attenuation within a stable, safe formula.
The cosmetic experience was an afterthought. Being heavy and leaving a white cast was ok if the SPF level was high.
Korean formulators began from a different premise.
In South Korea's intensely competitive beauty market, a sunscreen that feels unpleasant to wear simply won't sell.
Koreans care just as much about sun protection, but they also understand that a sunscreen should do so much more than just protect you from UV rays.
This commercial pressure drove Korean brands toward a formulation approach that treats sunscreen as an active skincare step instead of just a protective coating applied on top of skincare.
The result is that Korean sunscreens routinely include ingredient concentrations that are considered premium additions in a dedicated serum, let alone a sunscreen.
This includes hyaluronic acid, ceramide complexes, centella asiatica extract, and niacinamide.
The Isntree Hyaluronic Acid Watery Sun Gel is a perfect example
The formula contains eight distinct types of hyaluronic acid at different molecular weights, each penetrating to a different depth within the skin structure.
Low molecular weight hyaluronic acid reaches the dermis to support structural hydration.
High molecular weight hyaluronic acid forms a moisture-retaining film at the surface.
The sunscreen simultaneously protects against UV radiation and actively improves skin hydration throughout the day.
This matters because Diffey's research on application behaviour shows that when a formula actively improves your skin's feel and appearance throughout the day, you'll apply it generously and willingly.
The skincare-as-sunscreen philosophy produces better real-world UV protection and will keep your skin healthy and youthful.
What this means for your skin over time
There is a concept in photoprotection research called the cumulative UV dose.
This is the total amount of UV radiation your skin absorbs across a lifetime.
Single-day SPF ratings tell you almost nothing about this number.
What determines your cumulative UV dose is how consistently you apply it, how much you use, and whether you reapply when necessary.
Research on real-world sunscreen behaviour consistently shows the same pattern.
People who find their sunscreen cosmetically pleasant apply significantly more of it, apply it more consistently, and are more likely to reapply during extended outdoor exposure.
This is the long-term argument for Korean sunscreen that nobody makes clearly enough.
You want sunscreen use to be a daily habit that you maintain for decades, enabled by feeling the nourishing and moisturising effect when you apply it to your skin.
Korean sunscreen, absorbed in sixty seconds, leaves your skin looking better than before application. This removes every friction point that causes the habit to break down.
Your sunscreen is the only skincare product you will use every single day without exception for the rest of your life. It deserves to be something you genuinely want to reach for every morning.
If you want to know even more about what makes Korean sunscreen special, read my Complete Guide to Korean Sunscreen.
Sources
Green AC, Williams GM, Logan V, Strutton GM. Reduced melanoma after regular sunscreen use: randomised trial follow-up. Journal of Clinical Oncology. 2011.
Diffey BL. Sunscreens and UVA protection: a major issue of minor importance. Photochemistry and Photobiology. 2001.
Osterwalder U, Herzog B. Chemistry and Properties of Organic and Inorganic UV Filters. In: Lim HW, Draelos ZD, eds. Clinical Guide to Sunscreens and Photoprotection. Taylor & Francis Group, 2008.
Kullavanijaya P, Lim HW. Photoprotection. Journal of the American Academy of Dermatology. 2005.