Kids love to run around barefoot during the summer, but there’s at least one pesky problem that might turn your focus to your kiddo's feet. Plantar warts, skin growths that can show up on the soles of the feet, are caused by exposure to a strain of the human papilloma virus (a different strain than the one responsible for sexually transmitted disease), which thrives in moist, warm environments like public pools, showers and gyms. While these growths are benign, they can be painful and often have dark spots or blood clots in the middle. “Half of all children experience these warts,” says Oliver Zong, DPM, a New York City podiatrist. To keep your kids’ feet wart-free: Do change their shoes and socks daily. Don’t let them walk barefoot in public areas. Do have them wear water shoes when they’re at the pool. Don’t let them share shoes or sandals.