Surprising Facts About Skin Cancer CSI Dermatologists Want You to Know

Posted on: May 19th, 2025 by Our Team

Edited by Julia Kwan, MD

Skin cancer isn’t something we typically associate with glamorous reality shows like The Real Housewives of Beverly Hills. So, it was a sad surprise when Teddi Mellencamp, a Real Housewives alum and daughter of iconic rocker John Mellencamp, went public with the serious skin cancer challenges she’s been facing. Since 2022, when she first disclosed her melanoma diagnosis, she has had over a dozen cancerous moles removed from her back. In recent months, she reported the devastating news that the cancer has spread to her brain and lungs.

“These are all metastases of my melanoma,” she shared with the media. By making her cancer battle public, Mellencamp hopes to raise awareness and help others.

Because May is Skin Cancer Awareness Month, we’re amplifying her message. Because prevention is nearly everything when it comes to skin cancer – genetics and geography also play a role – we’re highlighting some surprising prevention facts beyond the basics of sunscreen, hats, and sunglasses.

Yes, You Need to Wear Sunscreen on Cloudy, Foggy Days and Indoors

If you’re going to San Francisco, be sure to wear sunscreen. It’s a myth that cloudy or foggy days mean no harmful rays. In fact, 80 percent of UV rays can still penetrate through gray skies. Sunscreen is also needed indoors, especially if you’re near windows, as UV light can pass through glass and still damage your skin. UV light, once thought harmless, contributes to skin aging and cancers. So, always apply sunscreen as part of your morning routine—think brush teeth, wash face, apply sunscreen.

Good news: although all indoor light sources—whether incandescent, fluorescent, or LED—emits some UV radiation, scientific studies to date report that the screens of our devices do not emit significant quantities of UV.

Sunscreens Do Not Cause Cancer

A few years ago, there was a scary rumor that sunscreens could cause cancer. But there is no scientific evidence that particles in sunscreen can penetrate a healthy skin barrier. Studies have found that despite concern about this, sunscreen ingredients don’t penetrate an intact skin barrier into the epidermis (the upper layer of the skin). On the other hand, we do know that if sunscreen is not used, harmful UV rays can cause skin cancer with increased risk in areas like California with long months of intense sunlight and lots of outdoor activities. A 2018 study from Australia, which has some of the world’s highest skin cancer rates, reported that regular sunscreen use can reduce melanoma risk by as much as 40 percent. CSI’s sunscreen products have all been formulated to meet our dermatologists’ specifications.

Applying Sunscreen and Insect Repellent Can Lower UV Protection

An intriguing new study from France reveals that mixing sunscreen with most insect repellents can reduce the sunscreen’s UV protection. The researchers cautioned that this raises concerns because many people use both products simultaneously during outdoor activities. This is the first scientific study to explore the effects of this combination.

As dermatologists, we recommend that you apply sunscreen first and wait for it to fully absorb. This gives the sunscreen time to form its own protective layer on the skin’s surface. Then, apply insect repellent. We do not recommend using products that combine sunscreen and insect repellent.

You Can Get Skin Cancer in Areas on Your Body Not Exposed to the Sun

Did you know that skin cancer can develop on areas of your body that are usually covered by clothing? It might start as a freckle or mole, but could evolve into skin cancer. How does this happen if there’s no sun exposure? Skin cancer begins when UV radiation damages the DNA in skin cells and cumulative UV exposure over many years can allow the abnormal skin cells to continue to mutate and progress to skin cancer. If not treated promptly, these cancerous cells may eventually spread through the bloodstream and lymphatic system to other parts of the body. It’s essential to have any suspicious mole or spot checked out by a dermatologist.

Plus, not all fabrics are created equal. Depending on the UPF (UV protection factor) level of the material of your clothing, you still may be getting UV exposure through your clothes. Porous cotton clothing is less protective than tightly woven polyester blend clothing; there is UPF-rated clothing that should be worn, especially if you are going to be out for extended periods of time.

Daytime Flight? Apply Sunscreen Before Takeoff

Flying can be a surprising source of UV exposure. A study published in the American Medical Association’s dermatology journal showed that at high altitudes, stronger UV radiation increases exposure through airplane windows. This is particularly true for passengers seated by windows during daylight flights. The exposure intensifies when flying over areas like snowfields, which reflect up to 85% of UV radiation. Pilots are at even higher risk due to prolonged exposure, but passengers should also be cautious. Always pack sunscreen in your carry-on—it’s an easy way to protect yourself during your flight.

Conclusion

Skin cancer is a mostly preventable condition, and awareness is key to protecting your skin. Prevention goes beyond wearing sunscreen—it’s about understanding the risks associated with UV radiation and taking steps to mitigate exposure. Whether you’re flying, sitting near a window, or simply out on a cloudy day, consistent use of sunscreen can significantly reduce your risk. Be proactive about your skin health and make an appointment for a skin check with your CSI dermatologist. It could make all the difference.