This article is part of The Skin Longevity Masterclass, an evidence-based series on how to keep skin healthy, resilient, and youthful across the decades. In Part 1, we explored skin as a longevity organ. Today, we turn to the most powerful external tool for preserving skin health — sunscreen and daily light protection.
When thinking of improving skin health and skin longevity, managing sun exposure is at the top on the list. Sun damage is probably the biggest factor of extrinsic skin aging for most people, especially when you consider that sun exposure occurs throughout our lifetime. Therefore, managing sun exposure is important for everyone: kids, adults, parents, and the elderly.
How Sunlight Damages the Skin
Other than just providing us warmth and light, sunlight also emits ultraviolet (UV) radiation. When these UV lights hits our skin, it triggers certain inflammatory molecules in our skin that degrade collagen and contribute to DNA damage. I want to focus on two different forms of UV radiation: UVA and UVB.
* UVA: this type of wavelength penetrates deep into the skin, creating damage via inflammatory reactions. These reactions break down collagen. UVA radiation is the primary UV light that drives skin aging.
* UVB: this type of wavelength can only penetrate the top layer of our skin, but directly damages the DNA of our skin cells. UVB is the main driver of sunburns and skin cancers.
Of note, melanin, the pigment in our skin, can protect DNA from this UVB damage. Darker skinned individuals, therefore, tend to have less issues with skin aging and skin cancers.
How to Choose the Best Sunscreen
Sunscreen is the best defense you have against the damaging effects of UV radiation. It reduces cancer risk through blocking UVB radiation and helps preserve collagen by reducing the inflammatory effects of UVA. But there are so many different products on the market — how do you choose?
Mineral vs Chemical Sunscreen
This is the first decision you have to make. Mineral sunscreens include zinc oxide or titanium dioxide on the ingredient label. These work as a physical barrier to scatter UVA and UVB rather than allow it to absorb into the skin.
Pros for Mineral Sunscreen:
* Photostable, so they don’t degrade as quickly in the sun
* Good for UVA and UVB radiation
* Best for sensitive skin or those with skin disorders like psoriasis or eczema
* Safe in pregnancy and for children
* More environmentally safe
Cons for Mineral Sunscreen:
* Much harder to rub in, often creating a white sheen on the skin. For darker skin tones, this can be a big problem.
* Hard to layer make-up on top of it
Chemical sunscreens often have avobenzone, octinoxate, oxybenzone on the label. These work by absorbing UV radiation and release it from the body as heat.
Pros for Chemical Sunscreen:
* Much easer to rub in, making them preferable for darker skin tones and for the face
* Feel lighter on the skin
Cons for Chemical Sunscreen
* Degrade quickly in the sun, needing repeat application
* Can irritate the skin
* Growing concerns surrounding systemic absorption into the blood stream and possible toxicity
* Damaging to the environment
Our preference is to primarily use mineral sunscreens as much as possible. If you need/want to use a chemical sunscreen, you could try products that contain a mixture of both mineral and chemical ingredients. At the end of the day, however, the best sunscreen is the one you will apply daily. If chemical sunscreen makes better sense for you, then go for it. It is better to be protected than not at all.
What Is SPF?
SPF stands for “Sun Protection Factor” and is a rating system for how well the sunscreen can block UVB radiation. It does NOT protect from UVA radiation. To protect from UVA radiation, you will need to use a mineral-based sunscreen or find a chemical sunscreen that also reads “Broad Spectrum” on the label, along with its SPF rating.
SPF 30 blocks 97% of UVB radiation and is my general recommendation for patients.
For children, those with a history of skin cancers or visible scars, those who have very fair skin, or those who work in the sun most of the day, I recommend SPF 50+, which blocks 98-99% of UVB radiation.
Keep in mind: no sunscreen is 100% effective, so we still need to be mindful of total daily sun exposure.
How to Best Apply Sunscreen?
Under application is probably the biggest problem when it comes to sunscreen. You don’t want to apply “just enough” but rather make sure the entire sun-exposed skin surface is well covered.
* For the face/neck: 1/2 teaspoon is a good volume. Make sure you get the ears!
* For the body: 1oz (shot glass size) is an appropriate amount
* If you are bald or balding, you will need to pay extra attention to the scalp.
Remember that both mineral and chemical sunscreens can wash off with swimming or sweating. Chemical sunscreens also degrade quickly in the sun. For reliable protection, you will want to reapply every 2 hours if outdoors.
What About Sunscreen While Indoors?
Sunscreen is still very important, even if you aren’t going to be outside that much. UVA radiation can penetrate windows of offices, homes, and cars, which drives chronic photoaging even if you never actually burn.
I recommend applying a mineral-based (or mineral/chemical mix) facial sunscreen that is at least 30 SPF every day before leaving the house. After applying it to your face and neck, make sure your hands are also covered. This will protect your face, neck, and hands (the three most sun-exposed areas of our bodies), prolonging a youthful appearance.
Sunscreen is not just for the beach — it’s the single most powerful tool we have to prevent premature skin aging and reduce the risk of skin cancer. By choosing a product you’ll use daily and applying it generously, you’re making one of the most important long-term investments in your skin’s health. In the next article, we’ll explore retinoids, another gold-standard strategy for supporting skin longevity.