The Sun Lover's Guide to Daily Sun Protection

The short version, if you only read one thing:

• The point of daily sun protection isn't to hide from the sun — it's to be in it more, without paying for it later.
• Use enough and reapply. About a shot glass for your body, every two hours. Under-applying is the mistake almost everyone makes, and it matters more than which sunscreen you buy.
• Check the UV index — it's already in your phone's weather app. Protect when it's 3 or higher; the sun is strongest from about 10 a.m. to 4 p.m.
• You don't have to choose between your skin and your vitamin D. Protect, and supplement if you need to.
• The best sunscreen is the one you'll actually reapply — which usually means one that feels good enough to wear every day.

---

Before having kids, Annmarie and I would spend every weekend in the summer exploring the parks and trails in southern New England and eastern New York.

We'd pick a spot, pull up a trail map and plot our route.

Parts of the Appalachian Trail, the Gunks in New Paltz, even Huntington State Park in our own town of Newtown. We sometimes run, sometimes hike, always bring a lunch to stop and enjoy at a lookout or in a secluded spot along the way.

At that time, I was in the camp that sunscreen is for people who are scared of the sun. The sun is naturally there, so shouldn't we naturally just be in it?

It sounds logical, but sometimes, I would definitely get burned. The back of my neck, my nose, the tops of my ears — and it hurt and eventually peeled.

Older now, I realize that these — among other instances where I got too much sun — were traumatic events for my skin, causing damage to it and in turn premature aging.

I wouldn't say my skin is in bad shape these days, but aging compounds, so we'll see as time continues on.

Knowing this, I'm now very aware of the flaw of my previous belief — just like too much water is bad or too much cold, or too much heat — so is too much sun. But, also, hiding from the sun keeps me away from some of the things I love so much that bring pure and needed joy in my life like skiing, tennis, hiking, and playing a game on the beach.

I've come to terms that now make sense to me and most likely will for you too: I don't protect myself from the sun. I protect myself so I can be in it. More hours, more days outside — without paying for them twenty years down the line. But it's still nuanced, I pack my sunscreen and my sunshirt and get an umbrella for the beach, but I still walk along it shirtless while I'm there.

So if you're anything like me, or just curious what the right way to approach the sun and sunscreen and still live a quality of life that gets you outside, you may find that a guide like this will give you the assurance that you're going to be OK.

It's a guide for people who live in the sun, not in spite of it. Everything below is the practical stuff — how much sunscreen, how often, how to read the one tool nobody uses, where the sun is actually good for you — and all of it ladders up to the same payoff: more time doing what you love outside.

Let's get into it. I'll start with what used to be true and then we'll work through my findings over the years to help you understand the most important parts — as well as the ones you can relieve yourself of.

Do you need sunscreen?

The short answer is, yes.

But like anything there is nuance.

Things have changed a bit since I was a kid in the 80s and 90s.

Back then, there was vanity in a good tan.

I remember laying out in the sun on the beach in South Carolina next to my mom and brother for hours. We would use sunscreen, but I would still burn. My cycle looked like this — burn the first day. Recover, sometimes even inside the next day or so. Then go back out the third day. Peel in 4-5 days. And by the end of the trip, notice that I had just enough bronze coming through the red that I was satisfied.

It's not a perfect process, but it was mine. And I'm sure it was for many. But these days, I am seeing some of the effects from this type of prolonged exposure. Even for those with darker skin, just because the tan came on sooner, it doesn't mean they were immune to the longer lasting effects.

What I'm sure of now is that less unprotected sun exposure is better — but, no sun is not.

The benefits of sun exposure are real. Good sun exposure does a few things for you. It's how your skin makes vitamin D. It pushes up serotonin — the daytime feel-good chemical that steadies your mood. And morning light sets your body clock, which is what lets you make melatonin at night, the hormone that actually gets you to sleep. (One common mix-up worth clearing up: the sun doesn't hand you melatonin directly. Daytime light raises serotonin, and your body turns that into melatonin after dark. Get your light in the day, sleep better at night.) And, just to reinforce what I mentioned before, most of the activities we do in the sun are for our enjoyment — or even if it's farming or driving — some type of meditation. So there is a psychological benefit beyond the physical.

So, yes, we need sunscreen and/or sun protection and there is science behind it.

Regular sun protection has some of the best evidence in all of preventive skin care supporting it. In a landmark Australian trial that followed people for years, those who used sunscreen daily had roughly 40% fewer squamous cell skin cancers than those who used it however they felt like it. In the ten-year follow-up, the daily-sunscreen group had about half the melanomas — and for invasive melanoma, the most dangerous kind, the reduction was even larger. That's not a product doing a small cosmetic favor. That's a daily habit changing the odds on the outcomes that actually matter. You can also extrapolate from this study that less cancer would also mean less damage to the skin — which means your skin would age at a slower pace with the use of daily sun protection.

Now on to the why…

Why does the sun damage your skin?

Two kinds of ultraviolet light reach you, and they do different things to your skin.

UVB is the burning ray. (The easy way to remember this is that the B in this is for burning.) It's the one that reddens your skin, and it's also the one that helps your body make vitamin D. It's strongest in the middle of the day and in summer.

UVA is the sneaky one. It's the aging ray (remember A for aging) and it goes deeper, it's the main driver of wrinkles and long-term damage, and it contributes to skin cancer too. Here's what makes it sneaky: UVA is up to 95% of the ultraviolet light that reaches you, it's roughly constant all day and all year, and it comes straight through glass. That soft light through your office window or your windshield on a gray afternoon? That's UVA, still working on you.

This is why "broad spectrum" on a label isn't marketing filler — it means the product is built to handle both, not just the one that burns. For now: you want protection against both, every day, not just at the beach.

What does broad spectrum really mean?

Here's the catch most labels won't explain: most common sunscreen filters are UVB specialists.

The main sun-policing ingredients in a lot of chemical formulas — octinoxate, homosalate, octisalate, octocrylene — are mainly there to stop the burning rays. They do little against UVA, the aging ray. There's really only one widely used chemical UVA filter in the U.S., avobenzone, and it has a quirk: it breaks down in sunlight. It degrades on your skin as you wear it unless the formula adds other ingredients to prop it up. So "broad spectrum" on a chemical sunscreen usually means a whole stack — a couple of UVB filters, avobenzone for UVA, and stabilizers to keep the avobenzone from quitting on you.

Zinc oxide skips all of that. One ingredient covers UVB straight through most of the UVA range, and it's photostable — it doesn't break down in the sun the way avobenzone does. (Titanium dioxide, the other mineral, handles UVB and the shorter UVA but tapers off on the deep UVA — zinc reaches further.) That's the whole reason we build around zinc: broad coverage and staying power from a single, gentle mineral instead of a Walter White chemistry set you have to keep balanced. It isn't the most potent filter drop-for-drop — which is exactly why how much you use and how often you reapply matters so much (more on that below). And yes, the tradeoff is real: non-nano zinc can leave a little white cast. Call it a fair trade — a few minutes looking faintly ghostly today so you're still a grape, not a Sun-Maid raisin, twenty years from now. (Our salt+blue, when applied correctly, has little to no white cast, BTW. You can read more here.)

When is too much sun, too much?

Let's break this one down. Because yes, you want to protect from UVA and UVB — but you also want the vitamin D your body makes when UVB hits your skin.

That part is real. It's not pseudoscience. Your skin makes vitamin D from UVB, and it self-regulates — you cannot overdose on the vitamin D you make from the sun. Here's the catch though: once you've made enough, further exposure breaks the excess back down. There's a ceiling to the upside.

So what does sunscreen do to that? For years the studies showed everyday use had little measurable effect on people's blood vitamin D. Then in 2025 the first proper randomized trial on modern high-SPF sunscreen — the Sun-D Trial — put a number on it: people told to apply SPF 50+ every day ended up about 5 nmol/L lower than people who used it at their own discretion. The effect is real. It's also modest, and here's what the researchers themselves said to do about it: keep using sunscreen, and supplement if you need to. I'd agree with them.

There's also a geography twist that settles more of this than sunscreen ever does. Above roughly 35°N latitude there's essentially no vitamin-D-making UVB in winter at all. In Boston, your skin makes basically none from about November through February no matter what you do — the sunlight is coming in at too low an angle. So for a big chunk of the country, for a big chunk of the year, sunscreen has nothing to do with your vitamin D.

One caveat worth noting: melanin is a built-in sunscreen, and the same pigment that blocks the burning rays also slows vitamin D production. The darker your skin and the farther north you live, the more a supplement might be needed.

Put it together and the answer is boring and freeing at the same time: protect your skin, and supplement your vitamin D if your levels are low. A year of vitamin D3 costs about the price of a couple of coffees. Sun damage doesn't come with a refund. You get to have both — you just get them from two different places.

How do you read the UV index?

A recent revelation for me involved reading the UV forecast. We were just in Sicily and our nephew would check the index every day and let us know what the number was.

We were intrigued. Why hadn't we been doing it? If the weather is cold, you put on gloves so you don't get frostbite on your fingers. When it's hot, you drink more water so you don't dehydrate. So if the index is low, you can stay out longer with, arguably less protection — and if it's high, be sparing with exposure and make sure you have tons of protection.

This is a great way to assess what a day outside may be like — in terms of your risk for sun damage — and it's easy to check — it's right in your smartphone's weather app.

It's a simple scale from 1 to 11+. The rule worth memorizing is this: when the UV index is 3 or higher, protect yourself. That's the threshold public-health agencies use, and it's usefully specific — it tells you a cloudy 68-degree day can still call for sunscreen, and a bright winter morning might not. The sun is generally strongest from about 10 a.m. to 4 p.m., which is when the index climbs.

Use it the way you'd use a surf report or a snow report — as information that helps you plan the day, not as a reason to stay in. Index of 8 and you're going to be out for hours? Bring the sunscreen, a sunshirt and plan a shady lunch. Index of 2 at dawn? Go enjoy it. The point of the number is to let you say yes to more, more intelligently.

Which sunscreen should I use?

One with mineral zinc, non-nano.

You already know why zinc — the last section was built around it. What's worth adding here is the "non-nano," and how zinc actually works. Despite how it's usually described, it doesn't mainly bounce light off your skin like a mirror; it mostly absorbs UV — it sits on the surface and handles the rays before they get in. "Non-nano" just means the particles are large enough to stay on top of your skin instead of sinking in. And it's gentle enough that zinc has been in diaper cream and wound care for a century.

A few things worth knowing when you read the back of a bottle. Plenty of sunscreens get padded out with cheap filler oils that thin the formula and stretch the margin without doing much for your skin. Anything water-based needs preservatives to keep bacteria from growing in that water — not evil, just what water plus time requires, and a reason a simpler formula has less to hide. And the whole category is a greenwashing minefield: "natural," "clean," "ocean-safe" get stamped on labels with almost nothing behind them. Be careful of the false prophets.

But the real selection rule is the one from the last section: the best sunscreen is the one you'll actually reapply. Feel isn't vanity here — it's the whole ballgame. A sunscreen that feels heavy or chalky is one you'll skip, and a skipped sunscreen protects nothing. So find one that feels good enough on your skin that reapplying it isn't a chore. For the full science, start with Is Non-Nano Zinc Oxide Safe? and The Real Difference Between Mineral and Chemical Sunscreen, and if you want to see how we built ours, that's our BODY mineral sunscreen.

How do you actually apply sunscreen? (this is where almost everyone fails)

I'm sure you have a story when you thought you put on enough, but you still burned. My own repeated story comes from when I didn't understand just how much you need to actually protect yourself. So if you take one section of this guide to heart, make it this one. Because the uncomfortable truth is that how you use sunscreen matters more than which one you buy — and most people, including people who care, get the how wrong.

Two numbers tell the whole story.

The first is the amount. The SPF on the front of the bottle is measured in a lab at a set thickness — 2 milligrams of sunscreen per square centimeter of skin. That works out to about a shot glass full (one ounce) for your whole body, and roughly a teaspoon, or two to three finger-lengths, for your face and neck. Most people apply somewhere between a quarter and half of that.

The second number is what that does to your protection, and it's worse than you'd guess, because SPF doesn't scale in a straight line. Protection rises exponentially with how much you put on — which means shorting it doesn't cost you a little, it costs you a lot. Apply half the recommended amount of an SPF 30 and you're not getting SPF 15. You're getting something closer to SPF 5 to 10. The fancy formula on the label is beside the point if it's spread too thin to do its job.

There's a coverage problem on top of the amount problem. On a single pass, people typically miss up to a fifth of their body — the ears, the back of the neck, the backs of the legs, the tops of the feet. The fix is almost comically simple: go over everything twice. A second pass cuts the missed spots dramatically.

So here are the application guidelines, and they're short:

• Use enough. A shot glass for the body; two to three finger-lengths for the face and neck.
• Cover everything, twice. Ears, neck, tops of feet, backs of knees. Do a second pass to catch what you missed.
• Reapply every two hours — and sooner if you've been swimming, sweating, or toweling off. "Water resistant" buys you 40 or 80 minutes, not a day.

This is the one place mineral and chemical sunscreens land in exactly the same spot: mineral can rub off, chemical can break down, and the fix for both is identical. Put more on. The best sunscreen in the world is the one you'll actually reapply. (But, remember, we're not putting on chemical sunscreens any more now that we know better.)

What else protects you from the sun besides sunscreen?

I love the saying, "when the only tool you have is a hammer, everything looks like a nail."

Sunscreen should not be your sun protection hammer. It can fail. You can be out too long, you can sweat it off, you can go swimming.

Here are some other sunscreen tools you can add to your tool kit to give you more freedom to be outside longer.

An obvious one, but shade is free and underrated: a tree, an umbrella, the shady side of the street at midday gets you real protection with minimal effort. Timing works with the UV index — the same afternoon is a very different exposure at 8 a.m. than at 1 p.m., and you get to choose.

Next, a hat with a brim does more for your face and neck than most people credit.

My favorite is UPF clothing. UPF — Ultraviolet Protection Factor — is the fabric version of SPF: it rates how much UV a garment blocks. A UPF 50 shirt lets through only about a fiftieth of the UV hitting it, and unlike sunscreen it never needs reapplying. A light long sleeve or a rash guard is protection you put on once and forget. I am notoriously wearing a sunshirt when others are not. On a fishing boat, at an all day outdoor festival, on the beach — do I stand out? Sure. But I rarely burn these days.

Finally, sunglasses protect the skin around your eyes and your eyes themselves, which sunscreen was never going to do.

None of this is about hiding. It's about having enough tools that being outside all day is a choice you can make freely, not a risk you're quietly running.

Extra bonus: A lip balm with SPF protection. Make extra sure this one is broad spectrum and does not have any nasty chemicals — since things on your lips most certainly can be ingested.

What should a daily sun protection routine look like?

I hope this has given you some assurance that being in the sun is more than OK. It's strongly encouraged — just with the right protection at the right times.

Here's the whole guide, reduced down to something you can actually work with, without thinking too much about it:

• Check the UV index (it's in your weather app). Three or higher, protect accordingly.
• Apply enough — a shot glass for the body, roughly a teaspoon for the face and neck — as the last step of your routine.
• Cover everything twice so you don't miss the ears, neck, and feet.
• Reapply every two hours, and after swimming, sweating, or toweling off.
• Supplement vitamin D if your levels are low — protect your skin and cover the nutrient separately.
• Use shade, timing, hats, and UPF clothing as extra tools, not as a cage.
• Then go live your life outside. That is the whole point.

Because that's what all of this is for. Not to keep you out of the sun — to keep you in it, on your terms, for as many years as you want. Protect well, and the trail, the water, and long afternoons are all still yours. That's exactly why we built the salt+blue BODY sunscreen.

Frequently asked questions

How much sunscreen should I use?

About one ounce — a shot glass full — for your whole body, and roughly a teaspoon (two to three finger-lengths) for your face and neck. The SPF on the label is measured using that amount, so applying less means getting significantly less protection than the number promises. Because protection rises exponentially with the amount applied, using half can drop an SPF 30 to closer to SPF 5–10.

How often should I reapply sunscreen?

Every two hours while you're out, and immediately after swimming, sweating, or toweling off. A "water resistant" label means the SPF holds up for only 40 or 80 minutes in water, not all day. Reapplication is the single highest-leverage sun-protection habit — it matters more than which sunscreen you choose.

Does sunscreen cause vitamin D deficiency?

Only modestly — and not if you manage your sun exposure smartly. Everyday sunscreen use has a small effect on blood vitamin D levels; the first randomized trial on daily high-SPF use (2025) found regular users had slightly lower levels and somewhat higher deficiency rates than discretionary users. The researchers' advice was to keep using sunscreen and supplement vitamin D if needed — not to stop protecting your skin. You also can't make vitamin D from winter sun above about 35°N latitude regardless of sunscreen.

What UV index means I need sun protection?

A UV index of 3 or higher is the threshold at which public-health agencies recommend protecting your skin. The index runs 1 to 11+ and is in most phone weather apps. UV is generally strongest between about 10 a.m. and 4 p.m.

Do I put sunscreen on before or after moisturizer?

After. Sunscreen is the last step of skincare — moisturizer first, then sunscreen, then makeup if you wear it. Give it a couple of minutes to settle before going outside. For reapplying over makeup, a mineral powder or spray is easier than lotion.

Is the sun ever actually good for you?

Yes. Sunlight drives your skin's vitamin D production, and preliminary research suggests it may also release nitric oxide that can briefly lower blood pressure. The goal of sun protection isn't to avoid the sun — it's to prevent sunburn and cumulative damage so you can enjoy the sun safely and often.

---

Kevin Gianni is the co-founder of salt+blue and Annmarie Skin Care and the author of Kale and Coffee. He's spent more than twenty years researching natural health and personal-care ingredients — reading studies, interviewing experts, and questioning dubious marketing. (He's also been using em-dashes well before AI made them suspicious, and has no intention of stopping.) More about Kevin.

---

References

• Green, A. et al. (1999), The Lancet — daily sunscreen reduced squamous cell carcinoma incidence ~40% (Nambour trial). Read the Nambour trial
• Green, A.C. et al. (2011), Journal of Clinical Oncology — regular sunscreen use, 10-year follow-up: total melanoma roughly halved, invasive melanoma reduced ~73%. Read the 10-year follow-up
• Tran, V., Neale, R.E. et al. (2025), British Journal of Dermatology — the Sun-D Trial: daily SPF 50+ vs. discretionary use lowered 25(OH)D by ~5.2 nmol/L; investigators advise continued sunscreen use plus supplementation. Read the Sun-D Trial
• Webb, A.R., Kline, L., Holick, M.F. (1988), J. Clinical Endocrinology & Metabolism — no cutaneous vitamin D synthesis in Boston (42°N) from November through February. Read the Boston latitude study
• Webb, A.R., DeCosta, B.R., Holick, M.F. (1989), J. Clinical Endocrinology & Metabolism — sunlight photodegrades excess vitamin D3 in skin; cutaneous production is self-limiting. Read the self-limiting synthesis study
• Holick, M.F. (2007), New England Journal of Medicine — an estimated ~1 billion people worldwide are vitamin D deficient or insufficient. Read the NEJM vitamin D review
• Liu, D., Weller, R.B. et al. (2014), Journal of Investigative Dermatology — UVA exposure mobilizes cutaneous nitric oxide and transiently lowers blood pressure. Read the nitric oxide study
• Faurschou, A., Wulf, H.C. (2007), British Journal of Dermatology — SPF rises exponentially with the amount of sunscreen applied. Read the SPF-dose study
• Heerfordt, I.M., Wulf, H.C. et al. (2018), PLOS ONE — a single application misses a median ~20% of the body; a second application cuts misses to ~9%. Read the coverage study
• Cole, C., Shyr, T., Ou-Yang, H. (2016), Photodermatology, Photoimmunology & Photomedicine — metal-oxide sunscreens protect primarily by absorption, reflecting only 4–5% of UV. Read the absorption-vs-reflection study
• World Health Organization & U.S. EPA — take sun-protection measures when the UV Index is 3 or above. Read the WHO guidance
• Lambert, G.W. et al. (2002), The Lancet — brain serotonin turnover rises with sunlight and hours of bright sun. Read the serotonin study
• Clemens, T.L., Adams, J.S., Henderson, S.L., Holick, M.F. (1982), The Lancet — increased skin melanin reduces the skin's capacity to synthesize vitamin D3. Read the melanin study
• Systematic review (2016), Photochemical & Photobiological Sciences — pooled UV-irradiation data find the skin-pigment effect on vitamin D is smaller and less consistent than long assumed. Read the pigment systematic review
• Avobenzone photostability (2021), Physical Chemistry Chemical Physics — avobenzone photodegrades under sunlight, losing UVA protection unless the formula stabilizes it. Read the avobenzone photostability study