What I've Learned About Sun Exposure Since My Skin Cancer Diagnosis

3 days ago

8 min read

In part one, I told you about my infiltrative basal cell carcinoma diagnosis at 41 and what that whole process looked like.

Here's part two: what the evidence actually shows about sun exposure, prevention, and what's genuinely in our control.

The sun isn't the enemy. Dose is what matters.

I moved to Florida because I love the sun. I hate cold, gray weather. Being outside genuinely energizes me, and getting a skin cancer diagnosis hasn't changed that.

Here's the thing about the sun: it's not "good" or "bad." Like almost everything else that affects your body, it's dose-dependent.

Drink eight cups of water a day and you're doing your body a favor. Drink eight gallons and you'll end up in the hospital. Same substance. Completely different outcome, depending entirely on the amount.

The sun works the same way. Too little exposure has real downsides. Too much has real downsides too. A 20-year Swedish study following almost 30,000 women found that women who actively avoided the sun had a mortality rate roughly double that of women with the highest sun exposure, and the difference was driven mostly by heart disease and other non-cancer causes, not by fewer skin cancer deaths. It’s important to note that this was an observational study, so it can't prove the sun itself caused the difference. But it's a real data point that "avoid the sun entirely" isn't automatically the safest instruction either.

"More sun equals more skin cancer" is too simple, especially for BCC

This is where it gets genuinely interesting, and it's part of what I've been digging into since my diagnosis.

Squamous cell carcinoma has a clean relationship with the sun: more cumulative lifetime exposure, more risk. It climbs steadily. It's even a recognized occupational disease for outdoor workers in some countries.

Basal cell carcinoma doesn't follow that same clean line. Research consistently shows BCC is tied more to intermittent, intense exposure (think sunburns, especially in childhood) than to total lifetime sun exposure. A meaningful share of BCCs show up on the trunk, a part of the body that gets a fraction of the sun your face or hands get. Studies on outdoor workers, who rack up enormous cumulative sun exposure, show an inconsistent relationship with BCC risk, in a way they simply don't for SCC. Sun exposure is still the leading known driver of BCC. It's just not as simple as "total time in the sun."

Hand applying white lotion to a sunlit leg in close-up, with warm skin tones and a relaxed outdoor mood.

If you did everything "right" and still got diagnosed, you didn't fail

I want to say this plainly because I felt it myself: a lot of people who get diagnosed with skin cancer feel like it's their fault. Like they slipped up somewhere, missed a spot, or didn't try hard enough with sunscreen.

The research doesn't support putting that weight on yourself. Genetics play a real role in BCC, independent of sun exposure entirely. Family history matters. A weakened immune system matters, people on immunosuppressive medication have dramatically higher rates of BCC, and more aggressive cases of it, regardless of how careful they are in the sun. Fair skin and phototype matters as well as prior radiation exposure.

That being said, it can truly happen to anyone. I was never irresponsible about being in the sun and I still ended up with an aggressive subtype of the most common skin cancer there is.

So, You Want to Be Smart About Sunscreen: Mineral vs. Chemical and what's actually going on your skin

Your skin is your largest organ, and it's not just a barrier. It absorbs things and that should be a consideration when you're applying a product to your entire body, every day, for decades.

There are two categories of sunscreen, and they work completely differently: Chemical sunscreens (oxybenzone, avobenzone, octocrylene, homosalate, octisalate, octinoxate) absorb UV radiation and convert it to heat. They tend to feel lighter and blend in more easily. They also absorb into your bloodstream. The FDA tested this directly in 2019 and again in 2020, and confirmed that all six of these common active ingredients show up in blood at measurable levels after normal use. What we don't fully know yet is what that means long-term. The FDA itself said this finding "calls for further industry testing," not that the ingredients are dangerous, but that the safety data doesn't fully exist yet for something applied to your whole body regularly for life.

Other countries have already acted on some of this. The EU caps the concentration of several of these chemical UV filters well below what's allowed in the US, based on their scientific committee's finding that the higher US levels weren't safe. The concern driving those limits: endocrine-disrupting effects at the concentrations commonly used in American sunscreens. These are human health limits, set by the EU's own consumer safety scientists, and they're stricter than anything the FDA currently requires.

Mineral sunscreens (zinc oxide, titanium dioxide) work differently. They sit on top of the skin and physically block or reflect UV radiation rather than being absorbed into it. They're not considered to enter the bloodstream in any meaningful amount. Zinc oxide and titanium dioxide are also the only two sunscreen ingredients the FDA has classified as "generally recognized as safe and effective," out of sixteen it evaluated.

Blue Lizard Sensitive mineral sunscreen tube, SPF 50, blue with gecko graphic, on white background.

This is why I choose mineral sunscreen when I have the choice. Not because chemical sunscreens are proven dangerous, they're not necessarily, but because when the safety data on long-term systemic absorption is still incomplete, I'd rather not be the case study. I care about what I put on my skin daily with the same scrutiny I'd give something I put in my body, because functionally, a lot of it ends up in my body either way.

Physical protection: the heavy hitter that doesn't rely on absorption at all

Sunscreen matters. But covering up is the most reliable form of protection there is, because it doesn't depend on reapplication, absorption, or whether you missed a spot.

A few things worth knowing:

UV radiation is strongest between 10am and 4pm. This is the window where the most damage happens the fastest. It doesn't mean avoid the outdoors, it means know when to be more deliberate about protection.
If you'll be outside longer than 20 to 30 minutes, especially during that window, physical coverage does more work than sunscreen alone. A wide-brimmed hat, UV-protective clothing, and shade create an actual barrier instead of relying on a product staying effective on your skin for hours.
Clothing with a UPF rating matters more than you'd think. There's a randomized controlled trial in young children showing that regularly wearing UPF 30-50+ clothing covering at least half the body prevented almost a quarter of the moles kids would otherwise have developed over three and a half years. Moles are a proxy for UV skin damage, so this is a meaningful signal that physical coverage genuinely changes outcomes, not just a good idea in theory.

I still spend plenty of time outside. I just think about when and how covered I am a lot more than I used to. And that’s something we all probably should be doing.

Nicotinamide: a promising option, not a guarantee

This one surprised me. Nicotinamide, a form of vitamin B3, has actual randomized controlled trial evidence behind it, which is rare for anything in the "supplement" category.

The ONTRAC trial put 386 people with a history of at least two prior nonmelanoma skin cancers on either 500mg of nicotinamide twice daily or a placebo for 12 months. The nicotinamide group had 23% fewer new nonmelanoma skin cancers overall. That's a real, statistically significant result.

Two important caveats, because I don't want to overstate this:

This trial was done in high-risk people who'd already had multiple skin cancers, not the general population. We don't have the same quality evidence for people using it purely as prevention before ever having a skin cancer.
When researchers broke the results down by cancer type, the reduction in squamous cell carcinoma reached statistical significance. The reduction in basal cell carcinoma specifically did not, even though the overall trend was in the same direction.

One more thing worth knowing: it's nicotinamide (also called niacinamide) you want, not niacin. Niacin is a different form of vitamin B3 that causes flushing and doesn't have the same research behind it.

I'd call this a genuinely promising, low-risk option worth a conversation with your dermatologist, especially if you have a personal history of skin cancer. I wouldn't call it a substitute for sun protection or annual skin checks. We also have to be honest with ourselves if we would be willing to take something like that 2x/day consistently. I know a lot of people who struggle with taking supplements regularly so it’s an important consideration.

Why a strong immune system still matters

It's tempting to assume that being generally healthy doesn't do much to protect you from something like skin cancer, the way it might for something like heart disease but your immune system is directly involved in catching and destroying abnormal cells before they become a real problem, skin cancer included.

The clearest evidence for this comes from organ transplant patients on immunosuppressive medication. Their rates of basal cell carcinoma run dramatically higher than the general population, and the tumors they do develop tend to be more aggressive. That's one of the most consistent findings in BCC research.

I'll be honest: I couldn't find solid evidence that general fitness or exercise specifically lowers BCC risk so I'm not going to tell you cardio prevents skin cancer, because the research doesn't back that up but I know that being stronger and healthier means I’ll be harder to kill so I’m going to keep on! ;)

What exercise does support is the underlying principle: a well-functioning immune system is part of your body's actual defense against abnormal cell growth. That's a reason to take care of your overall health, not because it guarantees anything, but because it's one more layer of defense working in the background.

What to actually do with all of this

Choose mineral sunscreen if the absorption question concerns you the way it concerns me. Look for zinc oxide or titanium dioxide as the active ingredient.

Build in physical protection, especially between 10am and 4pm or anytime you're outside longer than 20 to 30 minutes. A hat, UPF clothing, and shade do work that doesn't depend on reapplication.

Don't buy into "the sun is dangerous" or "sunscreen is all that matters" as an either/or. Dose matters more than either extreme.

Ask your dermatologist about nicotinamide if you have a personal history of skin cancer. It's inexpensive, low-risk, and has real trial data behind it, with the caveats above.

Don't carry guilt if you're diagnosed anyway. Genetics, immune status, family history, and pure intermittent bad luck all play a real role. You can do everything reasonably right and still end up where I did.

I'll keep sharing what I learn as I go through this. If this helped you think about your own sun habits differently, I'd love for you to share it with someone who needs to hear it too.

This post is for educational purposes and shares my personal experience and research. It is not medical advice and isn't a substitute for an evaluation by a licensed dermatologist. If you notice anything on your skin that concerns you, please make an appointment to have it checked.

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