Sun Protection Factor (SPF) indicates how well a sunscreen protects your skin from the dangerous effects of sunlight. The article discusses whether one needs stronger sunscreens for better skin protection.
Sunlight and Your Skin
Harmful Rays in Sunlight
- Sunlight is made up of many colours and invisible rays such as ultraviolet (UV) and infrared rays.
- UV rays are of high energy and can damage the skin in multiple ways.
- Ultraviolet radiation in sunlight is divided into three types depending on how they affect our skin: UV-A, UV-B, and UV-C.
- UV-B rays release their high energy in the top skin layer, causing skin burns with that concentrated burst of energy.
- UV-A rays cause other types of skin damage, such as breaking delicate structures inside the skin, causing wrinkles, sagging, and premature skin ageing. But we will discuss that in a different write-up.
In this article, when I refer to sunlight, I would be talking about UV-B rays.
Skin Damage by UV-B Rays
- UV-B exposure darkens your skin.
- Prolonged exposure can cause skin burns.
- Extensive exposure can increase the risk of skin cancer.
Vitamin D Formation Versus Skin Burns
UV-B rays help our skin manufacture vitamin D but they also damage the skin.
The duration of sun exposure needed for adequate vitamin D generation is about half of what it takes to burn the same skin.
You may have read on the ‘Internet University’ about how fifteen minutes in the morning sun are enough for vitamin D production. That is true for a fair-skinned person but not for a brown-skinned person. Here is my article with many references that show dark-skinned people need far more sun time: What is ‘adequate’ sun exposure for vitamin D?
Exhibit 1 below shows how sun exposure needed for vitamin D formation increases for people with darker skin.
Since the same rays cause skin damage, darker-skinned people can stay in sunlight longer in the same proportion without getting skin burns.
Think about this for a moment: If a brown-skinned lady needs one hour of sunlight to make adequate vitamin D, it would darken her skin noticeably. And two hours will burn her skin. No wonder getting enough vitamin D from sunlight is tricky.
How Do Sunscreens Work?
Sunscreens are lotions or creams that absorb harmful sun rays when applied to the skin. By the time sun rays reach your skin, they are considerably weakened reducing their skin damage.
Sun Protection Factor (SPF)
The sunscreen’s sun ray absorption ability, which indicates its protective capacity, is measured in terms of the Sun Protection Factor (SPF).
SPF tells you what fraction of UV-B rays reach your skin after you apply sunscreen. If a sunscreen with an SPF of 20 is applied, the skin will get twenty times less UV-B rays than when it is unprotected. So five per cent of rays reach the skin, while the rest are absorbed by the cream and filtered out.
So how much does SPF20 help? If a person has skin that can withstand sunlight for fifteen minutes without burning, it will be able to survive the same light for 20 x 15 = 300 minutes or 5 hours.
Thus, SPF20 offers two times longer protection than SPF10, and SPF30 three times longer.
Since people think that ‘more is better’, cosmetic companies heavily promote their products with higher SPFs and consumers also spend more money, in the hope of getting longer protection.
Is Higher SPF Better for Skin Protection?
Higher SPFs protect the skin longer. But does that mean we need them?
SPF10 will protect fair-skinned people for 2.5 hours, SPF20 for 5 hours, and SPF30 for 7.5 hours.
But sunscreens lose their efficacy after about two to three hours and need to be reapplied. This is especially true if you are out in the sun swimming or sweating. Luckily, if you are sitting indoors, you will not need to reapply them that frequently. But when indoors, you will not be getting sun exposure either.
The most likely scenario for most people is being outdoors for hours. While SPF20 and SPF30 may provide longer protection, you will still need to apply them again after three hours, just like SPF10. Won’t that be a waste?
Of course, a typical counterargument is that sun exposure for a shorter duration is also harmful and higher SPFs will protect better during those hours. Fair point!
What About Dark-Skinned People?
SPF20 helps a fair-skinned person withstand the sunlight for five hours. So for a brown-skinned person, whose skin can handle two hours of sun exposure without burning, SPF 20 will offer forty hours of protection.
Which part of the world has forty continuous hours of bright sunlight and which individual needs to remain in the sun for forty hours at a stretch?
And even if you take a much shorter stretch of time—say, a few hours—a low SPF product will do the job adequately unless you have very fair skin.
In summary, higher SPF sunscreens are not needed for brown- or dark-skinned people. Even a simple SPF15 sunscreen will be more than adequate.
For More Reading
- Wikipedia: Sunscreen
- US FDA: Sunscreen: How to Help Protect Your Skin from the Sun
- MedicalNewsToday: Which sunscreen should I use?
- US Environmental Protection Agency: UV Index
- Mayo Clinic: Best sunscreen: Understand sunscreen options
- On this Website: How to Prevent Wrinkle Formation
- On this Website: How to create any sun protection factor (SPF)
First Published on: 4th June 2023
Image Credit: pikisuperstar on Freepik