Key TakeawaysExposure to the sun’s rays can cause more than just sunburnsSunlight can also trigger hives, swelling and rashes These conditions are becoming more common due to extreme temperatures.TUESDAY, July 22, 2025 (HealthDay News) — Exposure to the sun’s ultraviolet (UV) rays is known to cause burns and increase risk of skin cancer and premature aging, but that’s not all it can do.Sunlight can cause more hives, swelling, and delayed, blistering rashes, George Washington University researchers warn. These conditions — collectively known as photodermatoses — are becoming increasingly common due to rising global temperatures.These disorders are often overlooked or misdiagnosed, even though they have distinct patterns, triggers and treatments, said Dr. Adam Friedman, professor and chair of dermatology at George Washington University School of Medicine and Health Sciences in Washington, D.C.There are several types of photodermatoses, he noted in a news release.Polymorphous light eruption is a mysterious bumpy rash that erupts on sun-exposed skin, such as the arms, chest, and neck, but not the face, Friedman said. Symptoms emerge within hours of exposure often resolve spontaneously within a few days of avoiding the sun. Solar urticaria is an allergic reaction to sunlight marked by hives that develop within minutes of sun exposure. Other symptoms can include dizziness or even life-threatening anaphylaxis. These symptoms resolve within 60 minutes of seeking shade.Photoallergic reactions are rashes that occur when sunscreens, fragrances or medications are activated by UV light.The best way to stave off these reactions is judicious use of a broad-spectrum mineral sunscreen, Friedman said. Wearing sun-protective clothing, wide-brimmed hats and placing a UV-blocking window film in cars also offer additional defense.People who develop photoallergic reactions should undergo testing to identify potential causes and take steps to avoid culprits, he said.More information The Skin Cancer Foundation has more information on sunscreen choices.SOURCE: George Washington University, news release, July 21, 2025 .What This Means For YouKnow the signs and symptoms of sun-related conditions and take steps to protect your skin..Sign up for our weekly HealthDay newsletter