The Harsh Truth About Sunscreen

The hidden dangers lurking in the way we protect ourselves from the sun

For years, the public message has sounded simple: the sun is dangerous, sunscreen keeps us safe, and a higher SPF means better protection.

We hear that message so often that we rarely stop to ask what we are putting on our skin, how much may enter the body, what happens when it washes into lakes and oceans, or how much plastic packaging is left behind. We might also ask whether seeing SPF 50 on a bottle makes us more willing to stay under the intense midday sun.

Despite decades of sunscreen use, rising SPF ratings, and public health campaigns, melanoma incidence in the United States rose from 8.8 cases per 100,000 people in 1975 to 28.26 in 2023, an increase of approximately 221 percent. This comparison does not show that sunscreen caused the increase, but it does deserve more thought than another automatic reminder to apply lotion.

Excessive ultraviolet exposure can damage skin and increase skin-cancer risk. Sunlight is also part of the environment in which humans evolved, and UVB exposure begins vitamin D production in the skin. The useful question is how much sunlight we receive, when we receive it, and what we put on our bodies to protect ourselves.

The Sun Is More Complicated Than a Warning Label

Ultraviolet sunlight reaches us primarily as UVA and UVB, and the difference matters. UVA penetrates deeper into the skin and contributes to premature aging, wrinkles, pigmentation changes, and long-term damage. UVB acts closer to the surface, causes much of the sunburn we recognize, contributes to skin cancer, and triggers vitamin D production.

You can sit beside a sunny window or drive for hours with sunlight streaming through the glass and still receive UVA exposure. Ordinary glass blocks most UVB, however, so it provides little meaningful vitamin D production. A window can therefore admit some exposure we would rather avoid without providing the benefit we expected.

Can SPF Give Us False Confidence?

SPF has become one of the most trusted numbers in personal care, but nobody applies sunscreen under laboratory conditions.

In daily life, people use too little, miss spots, sweat, swim, rub against clothing, dry off with towels, and may stay outside longer because a high SPF number feels reassuring. Even products labeled water resistant are tested only for short periods of 40 or 80 minutes. Sunscreen is not an all-day force field.

When a high SPF number replaces caution with confidence, it can change both behavior and exposure. Someone who might normally seek shade when the midday sun becomes uncomfortable may remain outside for hours because the sunscreen makes the risk feel managed.

Protection should reduce risk, not invite more exposure.

What Goes on Your Skin Does Not Always Stay There

Several widely used sunscreen filters, including avobenzone, oxybenzone, octocrylene, homosalate, octisalate, and octinoxate, can cross the skin barrier and enter the body. Sunscreen is therefore not always just a lotion sitting on the skin; some of its ingredients can become part of our wider chemical exposure.

Different countries permit, restrict, or ban different sunscreen ingredients, and concentrations and formulations change over time. Two bottles may display the same SPF 50 while containing very different chemical mixtures, so the number on the front tells you little about what is inside.

Modern Life Is a Complex Mixture

During a typical summer vacation, we may apply sunscreen while also taking medications or supplements, using cosmetics and fragrances, drinking alcohol, swimming in chlorinated water, breathing polluted air, eating food exposed to agricultural or packaging chemicals, and handling plastics. These overlapping exposures are part of ordinary modern life.

Scientists often study chemical safety one ingredient at a time, but that is not how we live. We encounter many substances year after year, often across large areas of skin and through repeated applications. One substance may also affect how another is absorbed, metabolized, stored, or eliminated.

Nanoparticles add another question. Mineral sunscreens may use nanoscale zinc oxide or titanium dioxide because smaller particles leave less of the familiar white coating, while sprays create a different exposure route because fine particles may be inhaled. When particle size is changed to alter how a material behaves, it is worth considering where those particles may end up.

Looking Past the Marketing

Sunscreen companies must generate revenue, protect market share, satisfy investors, and remain competitive. Their incentives are not the same as your interest in long-term health. Products are reformulated, ingredients are replaced, and allowable concentrations change, so yesterday's reassuring formulation may quietly become tomorrow's discontinued one while responsibility for long-term consequences remains unclear.

History offers plenty of examples of profitable products staying on the market while evidence of harm accumulated and meaningful action came years later. A company selling sunscreen is not an independent judge of the long-term consequences of using it.

I do not want to base my future health on reassuring marketing claims when the consequences of being wrong may appear decades later. I would rather read the ingredients, compare what different countries permit or restrict, notice when formulations change, and remember that commercial popularity says little about the effects of repeated exposure.

What Washes Off Does Not Disappear

When millions of people swim or shower, sunscreen can wash into waterways. Agencies such as NOAA have identified common sunscreen chemicals that can harm marine life, from coral reefs and algae to fish and sea urchins. These concerns are among the reasons Hawaii has banned the sale of many sunscreens since 2021.

Then there is the packaging.

Every summer brings another stream of plastic tubes, pumps, caps, and spray bottles. Those containers require resources to manufacture and transport before entering recycling systems, landfills, incinerators, or the wider environment.

Plastic does not simply disappear. Larger discarded items weather and fragment into smaller pieces, adding to the burden of secondary microplastics in soil and water.

The lotion on your body may be gone within hours, while parts of its environmental footprint can remain for decades.

Try This

Get morning light outdoors. Time outside soon after waking can help anchor the circadian clock and support daytime alertness. Outdoor light is much stronger than typical indoor lighting; there is no need to look directly at the sun.
Manage stronger sun later in the day. Pay attention to the UV Index, season, latitude, altitude, and time of day. UV is generally strongest around solar noon.
Use physical protection first when practical. Shade, lightweight clothing, and a broad-brimmed hat provide reliable protection without repeated chemical application or runoff into the environment.
Use sunscreen when physical protection is impractical. Examine the active ingredients instead of choosing a product solely because the label says SPF 50.
Account for real life. Swimming, sweating, exercise, friction, and towel drying reduce the protection you receive, so reapplication matters when you rely on sunscreen.
Protect your eyes and watch reflected UV. Choose sunglasses that block UVA and UVB. Water, sand, and especially snow can increase exposure through reflected radiation.
Treat sprays cautiously, including on cloudy days. Sprays can provide uneven coverage and introduce an inhalation pathway, while significant UV can still reach you through cloud cover.

Try This Summary

The aim is to use sunlight thoughtfully. Get outside for morning light to help anchor your circadian rhythm, then pay closer attention to UV exposure as the sun strengthens. Consider the UV Index, season, time of day, and how long you will be outside. Use shade, clothing, hats, sunglasses, and sunscreen when they genuinely add protection.

My Personal Routine

I do not use sunscreen as an automatic daily habit. Where I live, I usually keep deliberate sun exposure to about 20 minutes or less at a time, adjusting that according to the season, time of day, and strength of the sun. In January I may stay outside longer; in July and August, especially around midday, my exposure may be much shorter. The point is not the number 20 but adjusting to the conditions.

I prefer managing the amount of sunlight I receive rather than assuming a product can cancel out hours of exposure.

Not Everyone Has the Same Starting Point

Someone with very fair skin, a history of skin cancer, unusual sensitivity to sunlight, or medication that increases photosensitivity may need more protection. Children and people facing very intense UV conditions also require greater care. Skin pigmentation matters because melanin provides some natural UV protection while also reducing vitamin D production from the same amount of sunlight. There is no universal number of minutes that works for everyone; latitude, season, altitude, skin type, age, medications, and time of day all change the exposure.

Why It Matters

Modern sunscreen has been with us for generations, with SPF becoming established during the 1970s and increasingly sophisticated UVA and UVB protection following. Sunscreen then grew into an enormous consumer industry, while the US melanoma rate increased by approximately 221 percent between 1975 and 2023, leaving us with more than three times the incidence recorded at the beginning of that period.

During those same decades, international travel expanded, tanning beds became popular, populations aged, screening improved, diagnostic practices changed, and many aspects of our relationship with sunlight shifted. Put all of those facts on the table, and the idea that more sunscreen and increasingly high SPF numbers have solved our relationship with sunlight becomes difficult to accept.

Vitamin D Is Part of the Equation

UVB striking uncovered skin begins the process through which the body produces vitamin D3. Season, time of day, cloud cover, skin pigmentation, age, and other factors influence how much vitamin D sunlight can produce. Vitamin D supports calcium absorption, bone health, muscle function, and other biological processes, which is why treating all sunlight as something to avoid has never made much sense to me.

The sensible objective is to get useful exposure without staying out long enough to turn it into unnecessary damage.

Tanning Beds Are One Exposure I Would Avoid

I would avoid tanning beds because repeated users can develop skin that looks older than their age, with deeper wrinkles, uneven pigmentation, leathery texture, and loss of elasticity.

Natural sunlight already gives us enough ultraviolet radiation to manage carefully, so adding concentrated artificial UV exposure makes little sense to me.

What Not to Do

Do not use a high SPF as permission for prolonged exposure, or rely on sunscreen when timing, shade, clothing, or hats can reduce the UV dose more directly.
Do not assume one application lasts all day or that the absence of sunburn means no damage occurred. Water, sweat, friction, time, and UVA exposure all matter.
Do not assume legally sold ingredients are fully understood or remain only on the skin, particularly when formulations change and several widely used filters can enter the body.
Do not ignore the environmental cost. Sunscreen ingredients can harm aquatic organisms, while discarded bottles and tubes add to plastic waste that may eventually fragment into microplastics.
Do not treat sunlight through glass or tanning beds as healthy substitutes for controlled outdoor exposure. Windows largely remove vitamin-D-producing UVB while allowing more UVA through, and tanning beds deliver concentrated ultraviolet radiation by design.
Most importantly, do not hand responsibility for your long-term health to an SPF number, a marketing claim, or the company selling the product.

Bottom Line

Sunscreen was created to reduce a real risk, but it has become an automatic habit that deserves scrutiny. We repeatedly apply products whose ingredients can enter the body, wash into waterways, harm marine life, and add to plastic waste. A high SPF number may also encourage us to stay in strong sun longer than we otherwise would, even as US melanoma incidence has more than tripled since 1975.

I would rather begin with the sun itself by considering its strength, the time of day, the season, and how long I need to be exposed. Then I use shade, clothing, hats, sunglasses, and sunscreen where they genuinely add protection. The sun deserves respect, and anything we repeatedly put on our bodies deserves scrutiny.

These broader ideas about questioning everyday assumptions and making more informed choices about our environment are explored in Embracing My Vitality: Living Well in the Modern World, available worldwide through Amazon.

Technical Notes

UVA, UVB, and UVC

Radiation	Approx. wavelength	Main relevance
UVA	315–400 nm	Penetrates deeper into skin, contributes strongly to photoaging and pigmentation changes, and passes through many types of window glass.
UVB	280–315 nm	Acts closer to the surface, causes much of sunburn, contributes to skin-cancer risk, and triggers vitamin D production.
UVC	100–280 nm	Highly energetic but naturally absorbed by the atmosphere before reaching Earth's surface.

Sun Strength

UV intensity changes with solar elevation, latitude, season, altitude, clouds, ozone, and surface reflection. It generally becomes stronger closer to the equator and at higher elevations, while water, sand, and especially snow can increase total exposure.

SPF Is Not a Timer

SPF primarily measures protection against UVB-induced sunburn under standardized testing conditions. Actual outdoor performance depends on the amount applied, coverage, swimming, sweating, friction, towel drying, elapsed time, and reapplication. Water-resistant sunscreen is generally tested for either 40 or 80 minutes of water exposure, which is very different from all-day protection.

Sunlight Through Glass

Typical windows block most UVB while allowing considerably more UVA through. Sunlight through a window therefore provides little meaningful vitamin D production, while UVA exposure can still occur.

Systemic Absorption

Several organic sunscreen filters have been detected in systemic circulation after topical application, including avobenzone, homosalate, octinoxate, octisalate, octocrylene, and oxybenzone. Repeated sunscreen use therefore contributes to the body's overall chemical exposure rather than remaining solely on the surface of the skin.

Chemical Mixtures

Human beings are rarely exposed to one substance at a time. Sunscreen ingredients are encountered alongside medications, supplements, alcohol, cosmetics, fragrances, pesticides, plastics, food and water contaminants, air pollution, and countless other substances. The long-term consequences of these overlapping exposures are less understood than the individual chemicals considered separately.

Nanoparticles

Modern mineral sunscreens may use nanoscale zinc oxide or titanium dioxide because smaller particles make the product less visibly white on the skin. The exposure route matters, particularly with sprays, because particles remaining on intact skin are very different from particles that may be inhaled.

Environmental Effects

Several sunscreen chemicals can harm marine life, including coral, algae, mussels, sea urchins, fish, and other aquatic organisms. Hawaii has banned the sale of many sunscreens since 2021 because of concerns about specific chemical filters and their environmental impact.

Plastic and Microplastics

Sunscreen bottles and tubes are not themselves microplastics, but discarded plastic gradually fragments through sunlight, heat, abrasion, and weathering into increasingly small particles known as secondary microplastics.

Melanoma Incidence

US melanoma incidence increased from approximately 8.8 cases per 100,000 people in 1975 to 28.26 per 100,000 in 2023, an increase of approximately 221 percent. Over the same broad period, sunscreen use, SPF ratings, and public sun-protection campaigns expanded enormously, alongside major changes in travel, tanning behavior, population age, screening, and diagnosis.

Vitamin D and Vitamin K

UVB exposure to uncovered skin initiates vitamin D3 production, while vitamin D supports calcium absorption and normal bone and muscle function. Vitamin K activates proteins involved in bone metabolism and calcium handling, so the two vitamins participate in related biological systems while performing different roles.