SUNSCREEN 101: A Dermatologist's Guide To Everything You Need To Know
Here’s everything you need to know about UV RADIATION AND how to use SUNSCREEN like a pro.
As the weather gets warmer, we may be able to spend more time outdoors (at a safe #socialdistance, obvi), so now is the time to start thinking about sunscreen.
First, why use sunscreen?
There recently has been some publicity regarding the benefits of UV light and that sunscreen may not be as necessary as we have been led to believe. There is some early data that suggests UV exposure may be associated with a reduced mortality, but of course, science is complicated.
In my opinion (more on that here), these studies do not present strong enough evidence to overturn the VERY strong evidence that UV exposure is directly linked to the development of skin cancer. Not only is there a large body of strong scientific evidence linking UV exposure to squamous cell carcinoma, basal cell carcinoma, and melanoma, but many of my boomer patients (as I’m treating their skin cancers) tell me that they wished they had sunscreen rather than baby oil and iodine.
The World Health Organization (WHO) has deemed tanning beds carcinogenic to humans, as UV exposure leads to 450,000 cases of non-melanoma skin cancer and 10,000 cases of melanoma each year in the U.S., Europe, and Australia. This puts tanning beds into the same carcinogen category as cigarettes and arsenic as a cancer culprit. Check out the WHO for more information.
If avoiding cancer isn't reason enough to avoid the sun like the plague, it also is one of the main drivers of skin aging and wrinkles.
How does UV light damage our skin and cause skin cancer?
*I’m a strong proponent for giving my patients the knowledge of why I’m recommending something. Understanding the mechanism behind my recommendations will help motivate you to stay on track, hence the mini-science lesson.
UV light comes in a few different flavors, depending on its wavelength.
UVA (400-320 nm) is the main driver of photo-aging. It penetrates deeper into the dermis of the skin, damaging the collagen and elastin that gives your skin that youthful bounce. It can even pass through window glass, specifically tempered glass, which is used in passenger windows.
UVB (320-280 nm) doesn't go as deep (epidermis and superficial dermis), but is the cause of sunburns, a tan, and subsequently, skin cancer.
UVC (280-200 nm) is completely filtered by the Earth’s atmosphere and does not reach your skin.
On a cellular level, the DNA damage from UVB triggers a cascade of damage control processes, leading to inflammation, increased pigment production, and even skin thickening. Once you collect enough mutations over time, that's when skin cancers start to pop up.
What can you do to protect yourself from UV?
THE BEST WAY IS TO AVOID SUN EXPOSURE, especially in the middle of the day (10 AM to 4 PM).
The UV index can help guide you. It takes into account latitude, elevation, weather conditions, time of year and the ozone levels in your region and how it affects risk of UV overexposure. The higher the index, the higher the risk.
What role does sunscreen play in sun protection?
Sunscreen should be used when we go outside, but it's not an impenetrable shield. I have many patients that are surprised when they still get tan or even burned, when wearing sunscreen.
Using sunscreen in conjunction with sun protective clothing, like wide-brimmed hats, long sleeves and pants is the best way to protect your skin.
A UPF rating is a standardized measure of how much protection a certain piece of clothing gives you. I recommend looking for clothing with at least a UPF rating of 30, or even better, 50+.
How do I know which sunscreen to buy?
It may seem complicated, but it doesn’t have to be!
You will not lose if you choose a sunscreen that has these three things on the label (refer to the image on the left).
Do I choose a sunscreen with a physical or chemical blocker?
Okay, so if you’ve read this far, you are ready for a deep dive into the nitty gritty of sunscreens. Physical and chemical blockers refer to different types of active ingredients and the mechanism they use to protect your skin from UV exposure.
Physical sunscreens
The physical blockers are minerals that prevent UV light (both UVA and UVB) from hitting your skin by physically reflecting the rays away from you. It acts like a shield. Zinc oxide and titanium dioxide are FDA-approved to be used in sunscreens. I’m a huge fan of mineral sunscreens and here’s why.
PROS
Chemically inert
Safe with minimal to no systemic absorption
Protects skin from the full spectrum of UV radiation
More effective than chemical blockers for melasma
Less allergenic than chemical blockers (better for allergy prone or sensitive skin)
Tends not to sting when applied
CONS
Can be difficult to blend into darker skin tones and leaves a white cast (although there are many new formulations with micronized particles that are quite cosmetically appealing)
Chemical sunscreens
Chemical is not a bad word and chemical sunscreens are also very effective! The specific chemical structures absorb UV light and convert these high intensity rays into a lower energy wavelength that is not harmful to the skin. It basically acts like a sponge.
These chemicals vary in whether or not they address UVA or UVB rays, so they are often used in combination.
Common UVB blockers are octinoxate (octyl methoxycinnamate), octisalate (octyl salicylate), octocrylene, ensulizole (phenylbenzimidazole sulfonic acid).
UVA blockers include oxybenzone, Meradimate (methyl anthranilate), avobenzone (Parsol 1789), and ecamsule (Mexoryl SX).
PROS
Easier to blend into skin than mineral sunscreen
More often water-resistant
Wide variety of products
CONS
Can sting with application or if it gets into your eyes
Has more allergenic potential than mineral sunscreen
Most sunscreens use a blend of both physical and chemical blockers.
Ultimately, the best sunscreen is the one you will actually use!
Okay, so we’ve narrowed down how to pick a sunscreen, but what about what form it comes in?
Are creams better than sprays? What about those fancy powdered sunscreens?
The easy two-finger length rule for putting on sunscreen!
Besides personal preference, the main reason the form your sunscreen comes in matters is because it affects how much sunscreen gets onto your skin.
An adequate amount of sunscreen must be applied in order for you to get the stated SPF protection on the bottle. This is achieved by applying 2 grams of sunscreen per centimeter squared or a shot glass for all exposed surfaces.
Most people typically only apply 25% of the sunscreen they should, so they are only getting an effective SPF of 15 when they are using a sunscreen with SPF 60.
Using a cream or lotion makes it easier to measure out how much sunscreen you are applying.
An easy way to measure is to apply 2 finger lengths per body area (head and neck, each arm, front of the body, back, front of the leg, back of the leg). Getting adequate sun protection is WORK.
What about sprays?
Yes, spray sunscreens are way easier to apply than creams, especially if you are out and about at the beach or hiking. The ease also makes it easier to apply an inadequate amount of sunscreen with sprays since you can’t really see how much is actually getting on your skin.
Here are my tips for successfully using a spray sunscreen:
Spray each area for 6 seconds or make 3-4 passes
Avoid applying in a windy area
Hold the spray close to the skin (about the height of a fist)
Rub in the sunscreen thoroughly
Avoid spraying your face (don’t inhale the sunscreen)
What about powders and sticks?
I love sticks for the convenience, especially when traveling (you can carry them on!) and space is tight. I do have the same concerns about them. One study showed that sticks provide even lower density coverage than creams and sprays, so make sure you are making at least 3-4 passes with the stick.
For anyone that wears makeup, powders are a godsend when thinking about the age old dilemma of how to reapply sunscreen every two hours on top of a fully made up face.
Again, powders really don’t provide anywhere near the density of protection necessary, so don’t use it as your primary sunscreen. I only use it as a supplement to a wide brimmed hat and shade when I absolutely need to keep my makeup in place.
Other sunscreen tips and tricks:
Everyone has different things going on with their skin, and these guidelines will help further narrow down which is the best sunscreen for you!
If you are acne-prone, pick a non-comedogenic facial sunscreen.
If you have rosacea, stick to sunscreens with physical blockers, titanium dioxide and zinc oxide, only. They tend to be less irritating.
If you tend to experience stinging or burning when you apply sunscreen, avoid fragrance, chemical sunscreens, and try to use products with only titanium dioxide and zinc oxide. This also applies if you have allergies to sunscreens.
If you have melasma or another disorder of hyperpigmentation, stick to sunscreens with only physical blockers.
If you are a baby younger than 6 months, just stay out of the sun and cover the skin with clothing and shade.
If you are a baby older than 6 months, sunscreens with only titanium dioxide and zinc oxide, in addition to sun protective clothing, are recommended. These tend to be less irritating on baby skin.
What are my favorite sunscreen picks?
Here’s a run down of my favorite personal favorite sunscreen products:
(full disclosure: I have no financial interest in any of these companies)
I use EltaMD UV Clear and Neutrogena Hydroboost Water Gel Lotion when spending a lot of time outside, like for a hike, bike ride, or beach day. I’m looking for something that is light, absorbs well, and non-sticky. These two fit the bill for me.
I’m a minimalist, so my daily sunscreen needs to do double duty with a light tint and great sunscreen coverage.
The Nars Pure Radiant Tinted Moisturizer does both.
I love the EltaMD UV Aero because it goes on so well and has zinc oxide.
EltaMD UV Elements is one of the easiest mineral-only sunscreens to use. It rubs in easily without leaving a ghostly cast.
My male dermatology colleagues swear by Supergoop Unseen Sunscreen. It goes on sheer, without any sticky residue. The EltaMD UV Clear is also a dude favorite.
The Neutrogena Pure & Free baby line is mineral-only and a favorite of dermatologist moms. The stick is great to let your toddler self-apply (yay autonomy!) and bc it goes on white, you can see the spots they’ve inevitably missed.
Lastly, how safe is sunscreen?
In a nutshell, yes, sunscreen is safe for you to use.
A new recent study from the FDA showed that some chemical sunscreen ingredients, like avobenzone, are absorbed and found in the bloodstream when applied to the skin. However, there is no evidence at this time to show that these substances stay in the bloodstream for a prolonged period of time or have any toxic effects on the human body.
The FDA does not recommend that people stop using chemical sunscreens, but are asking for more studies and data to explore these findings further. Science takes time, is complicated, so the bottom line is that we shouldn’t jump to conclusions without adequate evidence. What we do know is that unprotected skin is at known risk for the development of skin cancers.
The FDA deems zinc oxide and titanium dioxide to be generally recognized as safe and effective (GRASE), so stick to mineral sunscreens if you prefer to err on the side of caution until we have more definitive data. The two sunscreen ingredients classified as not GRASE, PABA and tolamine salicylate, are no longer used in sunscreens sold in the U.S.
Overall, remember that sunscreens are regulated by the FDA as an over-the-counter drug and subject to extensive regulations (more so than cosmetics, most skin care products, and supplements).
So there you have it, everything you need to know (and maybe more) about sunscreen.
Now, go forth and frolic safely!
If you want more information regarding sun protection and sunscreen, check out the resources found on the American Academy of Dermatology website.
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References:
Broussard L, Hirner S, Dellavalle RP, Dunnick CA, Hugh J. Spray sunscreen: Characterizing application area density and implications for sun protection. J Am Acad Dermatol. 2020 Mar;82(3):749-751.
Young AR, Greenaway J, Harrison GI, Lawrence KP, Sarkany R, Douki T, Boyer F, Josse G, Questel E, Monteil C, Rossi AB. Sub-optimal Application of a High SPF Sunscreen Prevents Epidermal DNA Damage in Vivo. Acta Derm Venereol. 2018 Oct 10;98(9):880-887.