Sunscreen. The product that is touted as liquid gold among skincare enthusiasts, but neglected among… well, virtually everyone else.
There’s a lot I could explain on the topic of sunscreen, but being as much of it is pretty deep in the weeds, I will attempt to cut through a lot of the extra in this post and give you the simplified “how it works” version, as well as attempt to convince you why you should give sunscreen a try if you aren’t using it already.
First though, I’d like to alleviate some feelings I have on the topic.
Frequently, on skincare blogs and in skincare communities, sunscreen is touted as such a necessity that it is considered a pearl-clutching offense to even leave the house without it. Most sun damage is cumulative, and absolutely no one should be mocked for avoiding actual cancer, but there is a point where the insistence of some encroaches on the comfort of others. That is to say that while sunscreen is incredible, I am by no means pushing the usage of sunscreen on everyone. I understand that the filters bother some people, can aggravate existing conditions, and that sometimes… life happens. We don’t always have a bottle of sunscreen around when we need to dash out of the house. We don’t always want to slather it on before sitting outside to read a book. I certainly don’t.
And that’s okay.
Do what makes you comfortable, and live your life. Just be reasonable and safe about it.
With that out of the way, let’s dive right in, shall we?
Introduction to UV Radiation
You may remember the electromagnetic spectrum from science class and learning about radiation, such as light, heat, and radio waves. In short, it’s energy that’s moving. Leaving out a large portion of the electromagnetic spectrum for relevancy’s sake, there is light that we can see (known as the visible spectrum) as well as ultraviolet radiation.
The sun emits three types of invisible ultraviolet radiation known as UV-A, UV-B, and UV-C. UVC is filtered out completely by the ozone layer of the Earth’s atmosphere, but both UVB and UVA can reach the surface. While that may not seem so bad, climate change and depletion of the ozone layer has lead to an increase in UV radiation at the surface.
As you may remember from the previous post, the epidermis is comprised of several layers, including the stratum basal. This layer is enriched with epidermal stem cells (cells that can give rise to other cells of the same type), and give life to all epidermal structures, including sweat and oil glands as well as hair follicles. The layer beneath the stratum basal — the dermis — is also composed of stem cells that give rise to collagen and immune cells. These stem cells are essential to the skin as one of the systems of the body with a high rate of cell turnover.
When UVB radiation reaches our skin, our skin cells absorb the photons from the radiation, warping the DNA, rearranging nucleotides, and ultimately leading to defects. This damage causes a depletion of the epidermal stem cells, and ultimately, skin aging.  UVA can reach deeper into the skin, causing the most damage to our stem cells responsible for elasticity. This is why UVA damage is sometimes referred to as UV-Aging (with UVB as UV-Burning).
The skin attempts to counteract this damage by creating melanin (the pigment responsible for the color of our hair, skin, and eyes). Think of melanin as little umbrellas, attempting to shade the skin cells from the sun.
As sun exposure continues, the skin eventually begins to burn — the cells so damaged that they flake away and are discarded by the skin. The inflammation that follows is the presence of blood flow to the effected regions.
This is why even tanning — whether sun or tanning bed — is skin damage.
Surprisingly (or perhaps unsurprisingly), this damage begins to add up.
Visualizing Sun Damage
You may have seen the photo of the truck driver or even the video of what skin looks like in ultraviolet.
The epidermis thickens as a result of long-term exposure. The dermis loses elasticity. Inflammation occurs, parching the skin of essential moisture. This cascade of effects not only shows up later as wrinkles, but also can worsen eczema, acne, rosacea, or any other condition aggravated by dryness or inflammation.
And if we burn more than five times in our lives, our risk of skin cancer is doubled. According to the American Academy of Dermatology, 95% of melanoma cases are attributable to UV exposure. It is the most common type of cancer in the United States, with current estimates at 1 in 5 Americans developing skin cancer in their lifetime (or 9500 people every day).  You’re at an even higher risk of skin cancer on the driver’s side of your body, due to exposure while driving. 
If this isn’t enough, we can see changes in the structure of skin and it’s cells. According to a blog post by KindOfStephen, a group of researchers (with the funding of La Roche Posay) looked at the effects of UVB exposure on skin protected with high SPF (sun protection factor) and UVAPF (UVA protection factor) sunscreen as well as skin that was not protected.
To quote directly from KindOfStephen’s post: “What they found was that doses of UVB that caused long-lasting erythema (redness) caused morphological changes in the skin. Changes observed were spongiosis (abnormal accumulation of fluid), microvesicles, sunburn cells, and blood vessel dilation. None of these were observed in skin that was protected by the sunscreen.” 
So now that you know how ultraviolet radiation affects skin cells and you want to dip your toe into the sunscreen world, where do you even start? There are so many filters, so many ingredients, and you’ve even heard about sunscreen causing coral bleaching. Don’t worry, I’m going to get into these things, but first let’s break down the filters.
There are a large number of sunscreen filters available across the world. In the US there are only 16 approved filters, but only 8 are used, and out of that, only 2 of those protect from UVA.
Now you might be asking, “Wait, only two protect from UVA? I thought all sunscreen just protected me from the sun’s UV rays?” You wouldn’t be alone in this assumption. Even I thought this up until about 10 years ago.
Unfortunately, the United States doesn’t really have guidelines around UVA protection, unlike many other countries. In Asian sunscreens, the level of UVA protection is usually denoted by a PPD (persistent pigment darkening) rating, represented with plus symbols, such as ++++. In the EU and Canada, this is is simply a number. The higher the number (or the higher the number of plus symbols), the better the protection from UVA rays. Some sunscreen brands in the EU list their SPF along with the PPD value, ex. SPF 100/PPD 40. In the United States, we largely have to guess based on the percentage of listed filters or simply import them from other countries. I generally recommend sunscreens with high percentages of zinc oxide and titanium dioxide for this reason.
Below I’ve created a chart with the most common sunscreen filters you can get your hands on, along with their range, and some additional notes. For a more complete list of sunscreen filters, please refer to Skinacea’s UV Filters Chart . I’ve also included two of the sunscreens implicated in the killing or bleaching of coral. For a more complete list of that, please check out this BadgerBalm article .
Now I know what you’re thinking: why inorganic and organic? And furthermore, I thought zinc oxide and titanium dioxide were organic sunscreens and not the chemical variety.
The difference between these types of filters can be defined by chemistry. Titanium dioxide and zinc oxide do not contain carbon — they’re made of metal and oxygen, thus classified as inorganic.  However, both inorganic and organic filters work roughly the same — by absorbing the energy, bending, and eventually relaxing. Some filters do this better than others. For instance, avobenzone, as I noted above, must be stabilized by other filters. Instead of relaxing, avobenzone changes structure and breaks down, becoming more irritating to the skin. This is generally referred to as photostability, and while it is not typically harmful to wear a sunscreen that is unstable, it is just a bit of a pain, requiring re-application often and correctly to keep getting the amount of protection on the bottle.
Speaking of that protection, how do you know you’re even applying sunscreen right, or how much you should be using? Thankfully, science has an answer for just about everything.
Sunscreen Application and Care
Most sunscreens need to create a film over the skin in order to work effectively. This is particularly important for inorganic sunscreens, which are particle suspensions. This means you should be applying them evenly to get the best coverage and protection. Wait before applying any makeup to allow the sunscreen to dry down a bit and form a coating.
You also need to be applying the right amount to get the protection listed on the bottle. Yes, this even means your foundation or BB cream (which you should not be relying on makeup for sunscreen in the first place). Here’s a general guideline on how much you should be using on each portion of your body:
- Face: 1/4 teaspoon of sunscreen
- Neck (front and back): 1/4 teaspoon of sunscreen
- Arms: 1/2 teaspoon of sunscreen per arm
- Legs: 1 teaspoon of sunscreen per leg
- Chest: 1 teaspoon of sunscreen
- Back: 1 teaspoon of sunscreen
Applying less gives you less protection than listed on the bottle. For spray sunscreens, you need to apply several thin layers. Make sure to rub in each layer to avoid the streaky sunburn.
Sunscreens also have a shelf life of only about 3 years. Anything older than that should be tossed. Also be sure to keep your sunscreen in a cool place — even when at the beach. High temperatures of cars or direct sun will break down your sunscreen and render it less effective.
Lastly, re-apply your sunscreen when you are sweating or swimming. I know this is a pain, but if the two times I’ve burnt extremely bad in my life have taught me anything, it’s that the inability to sleep due to pain from sunburns can make the healing period one of the longest sets of weeks in your life.
- Darker skinned people don’t need sunscreen because they don’t burn. While it is true that caucasians have a higher risk of developing melanoma than the general population, skin cancer can affect anyone, regardless of skin color. In fact, skin cancer in patients with skin of color is often diagnosed in its later stages, when it’s more difficult to treat. They’re also less likely than Caucasian patients to survive melanoma, and are more prone to skin cancer in areas that aren’t commonly exposed to the sun, including under the nails. 
- Inorganic reflect sun rays, while organic filters absorb them. Both classes of filters work much the same, stretching, absorbing, and eventually releasing the energy. There is very little that is “reflected,” though inorganic sunscreens do have flashback (white cast under flash photography) due to their ability to reflect energy above the UV spectrum. 
- Inorganic sunscreen sits on the skin while organic sunscreens absorb. KindOfStephen put this best: “… if we want to protect ourselves from the rain we need to hold the umbrella above our heads. Sunscreens work the same way, you want them to absorb the energy before they can reach our skin cells, particularly the living cells. The most effective way for this to be done is to have them on the surface of the skin in a continuous and even layer.” 
- Sunscreens need time to activate on the skin. Sunscreens absorb UV due to their chemical makeup, not due to a chemical reaction that takes place on the skin.
- If I wear sunscreen, I won’t get adequate vitamin D. Vitamin D is very important to our bodies, and many people are deficient in it. However, thanks to the many well-formulated vitamin D supplements on the market today, we can get D3 just as efficiently as if we were sitting in the sun for an hour. Check with your doctor before taking any supplements.
- Glass blocks all UV. Glass only filters UVB rays, so you still must wear sunscreen to be protected from the most harmful rays — UVA.
General Sunscreen Guidelines
- Apply your sunscreen after moisturizer and before makeup. Think of it as the barrier that protects your skin from the outside. I typically apply my sunscreen as the last step in my AM routine and do my eye makeup while I wait for it to sink in.
- Apply your sunscreen under your eyes. Avoid the top of the lid, which can get oily and cause the sunscreen to “run” into your eyes later in the day. Protection of the delicate undereye area prevents darkening that can look similar to undereye circles, as well as premature aging and wrinkles.
- Wear sunscreen, not moisturizer with SPF or makeup with SPF. As I mentioned above, sunscreen in moisturizer or makeup is not adequate.
- Don’t neglect your driver’s side. It’s easy to forget about our bodies, but as I mentioned, skin cancer is especially common on the driver’s side of the body. Avoid this with sunscreen, UV protective clothing, or special UV tinting.
- Wear at least SPF 30, but don’t worry about trying to wear SPF 100. There is very little difference between the amount of protection that SPF 30 provides versus SPF 100, when applied correctly. For example, SPF 30 blocks nearly 97% of UVB rays, while SPF 50 blocks an estimated 98% of UVB rays.  On top of this, higher SPF values mean more filters, which can irritate some skin. Good guidelines are at least SPF 30 but no more than SPF 50.
- Wear the highest amount of SPF you can tolerate. For some, this is SPF 15, and that’s okay. Whatever your skin can tolerate is better than nothing at all.
- When in doubt, wear a hat. There are plenty of UV-protective clothing options (and UV-blocking umbrellas!) on the market today. When I know I am going to be out in the sun for a long period of time, I will frequently bring a hat with me in addition to my sunscreen.
- Wear sunscreen and avoid the sun if you’re especially sun sensitive. This means skin with acne, rosacea, eczema, psoriasis, or under the treatment of photo-sensitizing (sun sensitivity) ingredients like retinol, retinoids, isotretinoin (Accutane), benzoyl peroxide, AHAs like glycolic acid or lactic acid, and topical steroids (such as triamcinolone).
- American Academy of Dermatology – Skin Cancer
- Kind of Stephen – Visualizing how a daily sunscreen can protect the skin from UV damage
- Study: Driving May Contribute to Left-Side Skin Cancers
- Ultraviolet Radiation-Induced Skin Aging: The Role of DNA Damage and Oxidative Stress in Epidermal Stem Cell Damage Mediated Skin Aging
- Skinacea – UV Filters Chart: Sunscreen Active Ingredients
- BadgerBalm – Coral Reef Friendly / Reef Safe Sunscreen
- Kind of Stephen – “Physical” vs. “chemical” sunscreens and other sunscreen myths
- Skinacea – How much sunscreen should I apply?
- The Derm Blog – Is that sunscreen in your car still good?
- Skin Cancer Foundation – Does a higher SPF sunscreen always protect your skin better?