You probably slather sunscreen on your shoulders, your nose, maybe even the tops of your feet. But when was the last time you thought about protecting the skin underneath your swimsuit – specifically, the parts that today’s trending cuts barely cover? Most of us assume that if a body part has always been hidden from the sun, it’s somehow safe. Skin specialists say that assumption is not just wrong; it may be creating a new frontier of risk we are only beginning to understand.

The swimwear trend nobody is talking about honestly

Cheeky-cut bikini bottoms, high-cut legs, and string configurations that leave the gluteal region almost entirely bare have become standard across retailers, with mainstream appeal extending well into the Gen Z consumer base. These styles are everywhere – on beaches, in ad campaigns, across social feeds. Yet the skin being revealed often has no history of sun exposure and correspondingly no tolerance for it. The lower buttocks, posterior thighs, and perianal area are regions that can receive intense intermittent UV exposure during beach and pool activities without anyone giving it a second thought.

This is not a brand-new concern. A 1986 case-control study found that women who wore bikinis or bathed nude between the ages of 15 and 24 had a rate ratio of 13.0 for trunk melanoma compared with those who wore conservative one-piece suits, after adjusting for constitutional risk factors. Decades later, minimalist swimwear is no longer just an option – it is the dominant trend. So why aren’t we hearing more about the dermatological implications?

A landmark Swiss epidemiologic analysis identified the buttocks as a site of minimal melanoma risk for both sexes, precisely because they historically received virtually no UV exposure under conventional clothing and swimwear. The same study noted that melanoma risk at various body sites closely tracked sex-specific differences in clothing patterns and recreation habits: trunk melanomas were more common in men, and leg melanomas in women, reflecting where each sex received the most intermittent UV exposure. When fashion shifts that equation, risk shifts with it.

What happens when UV-naive skin meets intense summer sun

The biology here matters. Melanomas arising on intermittently exposed sites are more likely to carry BRAF mutations, a specific genetic change linked to cancer growth, and occur in the context of higher nevus density – meaning more moles. This suggests a distinct cancer-causing pathway triggered by episodic, intense UV insults rather than cumulative daily exposure. The American Cancer Society has specifically linked trunk and leg melanomas to recurrent sunburns, particularly those occurring in childhood and early adulthood.

When a body region that has been UV-naive for decades is suddenly and repeatedly exposed to high-intensity summer sun without sunscreen, it may behave like intermittently exposed skin, carrying all the associated cancer-promoting implications. For people with a high number of moles, fair complexions, or a personal or family history of melanoma, this represents a clinically meaningful change in risk.

Kelly English, a mid-40s outdoor adventure guide of Irish ancestry – a demographic with among the highest UV sensitivity – learned this firsthand. After starting CrossFit in the summer of 2024, she noticed an irritated mole on her lower back and, while examining it, spotted a lesion in a place most people never inspect. A biopsy confirmed stage I superficial spreading melanoma at the center of her buttocks. She had spent years leading bike and hiking expeditions and working on the production of a major television series filmed extensively in tropical locations, all without consistent sun protection. She had never had a full-body skin check before her diagnosis.

A generation primed to underestimate the danger

The exposure gap is being compounded by a wave of UV misinformation. A 2024 American Academy of Dermatology survey found that 37% of Gen Z adults were unaware of one or more sunburn risks, and 57% endorsed common tanning myths, including the belief that a base tan protects against further UV damage. Approximately 34% said achieving a tan was more important to them than preventing skin cancer. Half reported being sunburned at least once in 2024, and 10% reported blistering burns.

Social media is accelerating the problem. A 2024 Orlando Health Cancer Institute survey found that 14% of adults younger than 35 believed daily sunscreen use was more harmful to skin than direct sun exposure, while 23% believed staying hydrated could prevent sunburn. These myths are meeting a fashion moment that leaves more skin exposed than ever – a combination dermatologists are watching with growing concern.

English’s surgical recovery also reveals a complication most people would never anticipate. Following wide local excision of her melanoma, her wound failed to heal, became infected, required reopening, and necessitated weeks of wound packing before reclosure. Standard margins for stage I melanoma require excision to subcutaneous tissue, and for deeper lesions to fascia, producing wounds that may be several centimeters wide in tissue that moves with every step. Wound dehiscence, infection, and the need for repacking are not rare outcomes in the gluteal area.

What you can actually do about it

Board-certified dermatologist Whitney Hovenic, MD, of the Skin Cancer and Dermatology Institute in Reno, Nevada, sees an opportunity to evolve the protection conversation. She has noted that changing fashion trends may be shifting sun exposure patterns, and that these styles are not going away anytime soon – meaning we need to adapt our approach. Total-body skin examinations by a dermatologist remain the most reliable way to detect lesions in hard-to-see locations like the posterior trunk and gluteal region.

The takeaway is straightforward. If your swimwear is showing skin that has rarely or never seen the sun, that skin needs protection – sunscreen, reapplication, or UPF coverups when you are not in the water. And a full-body skin check, the kind where a dermatologist examines every inch including the areas you cannot easily see yourself, is worth scheduling before another summer passes. You now know something most beachgoers do not: the places we forget to protect may be the ones that need it most.