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The past 50 years have seen a rapid evolution in medical opinion on sun exposure. My mother told stories of spending entire summers lying on the beach coated in baby oil. By the time I was a kid, we did use sunscreen, but I got at least one terrible sunburn every summer, and once ended up with giant sunburn blisters on my face.

In contrast, my children live in sunscreen and hats. When they were babies, they wore long-sleeved bathing suits. One of my children has sunscreen in the water bottle pocket of their backpack.

This change in behavior has been prompted in part by the growth in skin cancer rates and the growing sense that sun exposure and skin cancer are linked. According to the Skin Cancer Foundation, treatment of non-melanoma skin cancers in the U.S. increased nearly 77% between 1992 and 2006, and melanoma diagnosis increased by 1.9% annually between 2000 and 2009. To parents, dermatologists and general pediatricians emphasize the importance of sun avoidance and sunscreen usage.

But there is backlash. Parents are worried about high levels of chemical usage, and note that we all turned out fine despite the sunburns. Is it really necessary, people wonder, to be quite so obsessive about this? And increasingly, I have been hearing concerns from people that sunscreen itself might cause cancer, maybe even skin cancer.

What does the data say?

Take me to the bottom line

Does sunscreen use prevent skin cancer?

A big pitch for sunscreen (or sun-protective clothing) is skin cancer protection. This link is widely understood, but the direct evidence is more limited than you might think. The theory is clear — we know that sunburns cause skin damage, and that skin damage can cause problematic cell behavior. Beyond that, we know that skin cancer is more common in locations with more sun exposure, suggesting that sun exposure matters.

But what we lack is compelling data showing that the use of sunscreen mitigates this link. There is one randomized trial in Australia that showed a reduction in melanomas for people who were randomized to the sunscreen group. However, this effect is only borderline in its significance, and a 2018 meta-analysis found no evidence of a link between sunscreen usage and decreased skin cancer rates.

There are limitations to this analysis, and non-cancerous skin damage clearly occurs with sun exposure. Even without a smoking gun on the most serious types of skin cancer, it would be a mistake to dismiss this potential benefit, even if it is probably not large.

Alongside this evidence on sunscreen and skin cancer, you will occasionally see the claim that sunscreen causes skin cancer. This is based on a faulty understanding of data. People who are at risk for cancer may wear more sunscreen, and in addition, wearing sunscreen may give a false sense of security. There is no data that would point to sunscreen causing skin cancer.

There is also a clear benefit to sunscreen, which is that you do not get sunburned. Getting sunburned isn’t fun. It hurts, your skin peels, and you look like a lobster. Given the short-term nature of children’s horizons, I find the specter of temporary pain is more useful as a motivator than long-term risks.

To get these benefits of sunscreen, you do not need to have SPF 100, or whatever is the upper limit of what they are selling these days. The U.S. Food and Drug Administration has acknowledged there is no evidence that raising SPF above 50 makes any difference.

Are there risks to sunscreen?

I want to turn now to the more contentious question of sunscreen risks.

First, let’s right-size the scope of the risks. There are three ways to protect from the sun: clothing, mineral sunscreen, and chemical sunscreen.

Regular clothing generally provides some sun protection. UPF clothing is specifically made with fabrics that block ultraviolet (UV) rays. Other than getting hot, wearing clothing to protect from the sun has limited risks. (In fact, it’s an ideal option for babies under six months, where you may want to limit the amount of sunscreen and minimize their sun exposure with clothing, hats, and shade.)

Mineral sunscreens rely on mineral filters, like zinc oxide or titanium dioxide, to block the sun. They are typically thick and leave a white cast on your skin, but they provide sun protection and are not subject to some of the health concerns that people raise about chemical sunscreens.

Chemical sunscreens work by using chemicals to block UV light. They tend to be popular because they are convenient, easy to spray, and do not turn your face white. But these are the products that raise consumer worries.

The primary health concern with chemical sunscreen is that the active ingredient, oxybenzone, is dangerous. The concern is about disruption to the endocrine system. Such disruptions could impact puberty, fertility, hormone development, and possibly cognitive function. The endocrine system is very important.

There is a reasonable body of evidence from mice and rats that such disruptions happen. When rats are fed this type of chemical, it affects their uterus size. Evidence from mice shows that exposure of pregnant mice (again, through food) impacts endocrine markers in their offspring. Given our biological understanding of these chemicals and their impact in cell experiments, this is plausible.

It is always challenging to port evidence from mice and rats into people. People are much bigger than mice, and it is difficult to figure out how doses relate. Most rodent studies use doses that far exceed human doses. Follow-up work to the first rat study above suggests that you’d need decades of full-body daily sunscreen usage to match the rat dosage.

In contrast, we have little direct evidence of these impacts in people. One 2017 summary study reports some mixed associations between birth weight and UV-blocking chemical exposure in utero. These birth weight differences are very small, and the authors do not see any other impacts. This doesn’t mean there aren’t effects; we just do not have positive evidence that they are there.

Overall, it seems likely, based on the animal evidence, that at some level sunscreen chemicals would be harmful. The question is whether these levels are common or possible with normal levels of exposure among people.

Speaking to this, a 2020 study evaluated how everyday use of sunscreen impacted chemical levels in the bloodstream. The authors had people apply a lot of sunscreen — 2.5 tablespoons every two hours over 75% of their body. What they found was that the chemicals from the sunscreen were absorbed into the body and persisted past the end of the study period. The levels of chemicals in the bloodstream were higher than the FDA limit for presumed safety, which has led to a need for ongoing work. Importantly, this paper did not conclude that sunscreen was unsafe.

What about vitamin D?

A concern with any type of sun avoidance (including clothing and mineral sunscreens) is that we will not get enough vitamin D. Your body produces vitamin D from UV light exposure, so it is correct that if you do not have that exposure, you will produce less vitamin D. In principle, this could lead to a deficiency.

However, this type of deficiency in kids is very rare in the developed world today. Many foods are supplemented with Vitamin D, including milk, so your child is likely to have a sufficient amount. In other words, getting Vitamin D is not a reason for them not to wear sunscreen.

The bottom line

• Sunscreen helps prevent sunburns. That is enough of a reason to use it, and you don’t need an exceedingly high SPF rating — there is no evidence that an SPF above 50 provides more sun protection.
• Sunburns cause skin damage, and skin damage can cause problematic cell behavior, but there is a lack of compelling data to suggest that the use of sunscreen itself prevents skin cancer. There is also no evidence that sunscreen causes cancer.
• Unlike mineral sunscreens that rely on filters like zinc oxide to block the sun, chemical sunscreen works by using chemicals to block UV light.
• The main concern about chemical sunscreen is about the ingredient oxybenzone and its potential disruption to the endocrine system. There is a reasonable body of evidence from mice and rats that such disruptions happen, but at this point we have little direct evidence of these impacts in people.
• A concern with sun avoidance is that we will not get enough vitamin D. A childhood deficiency in Vitamin D is unlikely and not a reason not to wear sunscreen.