I’d gotten roped into running a few days of the TransRockies Run, which traverses 120 miles across the high peaks of Colorado over a six-day sufferfest that climbs 20,000 misery-inducing feet. I’ve always loved trail running, but this was a whole new level for me, logging between 13 and 24 miles a day and climbing up and down seemingly endless switchbacks. Somewhere in the midst of a six-mile descent on day one, I started feeling a burning pain in my right heel. My legs and lungs felt sturdy, but my feet were crumbling. I thought I’d done everything right. I’d been training in the same pair of high-end trail running shoes for weeks and I wore technical, breathable socks. It wasn’t like I showed up in a brand new, too-small-for-me shoes. The rubbing got worse and by the time I crossed the day’s finish line hours later, all I could think about was the stinging coming from my foot. Forget the high-alpine vistas, the gurgling creeks, the exuberant faces of fellow runners—I was just surviving, praying I could make it to the finish without amputating my own foot. In the finish area, I collapsed on the dirt, devoured a giant slice of watermelon, and carefully peeled off my shoe and sock. The skin had been rubbed raw in a pink, fleshy mess: It was the blister to beat all blisters. While I was feeling sorry for myself, I spotted ultrarunning celebrity Dean Karnazes, whose book, “Ultramarathon Man,” I’d read not too long before. He’d, of course, finished hours before me, but he was perched nearby. He removed his shoes, too, and much to my surprise, he started inspecting his feet. He had a blister, too. All of which is to say, blisters can be fun-sucking and brutal and they don’t impact just the uninformed and poorly trained. The tiniest blister can take down even the strongest runner and ruin the grandest adventure. So I set out to get to the bottom of the blister mystery: How do they form? How do you treat them? And most importantly, how can we stop them from ruining our feet in the first place?  When Heather Anderson broke the speed record on the 2,650-mile Pacific Crest Trail in 2013, averaging 44 miles a day and completing the Mexico-to-Canada self-supported thru-hike in just 60 days, the blisters on her heels formed on day two and persisted the entire hike. The first one popped on day 14, then re-formed and popped again, and so on, for three months straight. The pain of her swollen, aching feet would startle her awake at night. “I’d never dealt with blisters before,” Anderson said. “It must have been the heat and the extreme miles. I had one on each foot, on either side of my heels. They were about two inches long and very painful. I just learned to ignore them after a certain amount of time.” Or take long-distance runner Dusty Olson, who used to pace ultrarunning phenom Scott Jurek. Years ago, on a multi-day run on Minnesota’s 310-mile Superior Hiking Trail, Olson wore a pair of cheap, cotton socks and paid the price. “My toes were raw and blistered and I also got a blister on my heels,” Olson says. “Sometimes it was a sharp, deep pain that made me want to stop.” Olson, of course, learned to use better socks (he now prefers a merino wool lycra blend) and he uses a wax-based lubricant (like RunGoo) between his toes. Utah-based ultrarunner Karl Meltzer suffered deep blisters while attempting to break the speed record on the Appalachian Trail in 2014. “It was the size of a quarter, not terribly big, but I had enough fluid in that thing to make a cocktail,” Meltzer says. “It caused problems for the next 15 days. Running 50 miles a day, it did not heal quickly and it hurt daily for every mile.”  Blisters are caused by pressure, friction, heat, and moisture. Combine that with the movement of your foot inside your shoe over an extended period of time, and bam: Welcome to blisterland. “Even a blister the size of a pea in the wrong spot can disrupt your gait, which goes up your knees, your back,” says John Vonhof, author of the book, “Fixing Your Feet: Prevention and Treatments for Athletes.” “It’s your feet that get you from the start to the end. If your feet hurt, everything goes downhill. Your feet are your foundation.” Vonhof is a former paramedic and ultrarunner who now works in the medical tents at races like the 100-mile Western States Endurance Run in the Sierra Nevada and Badwater, a 135-mile race in Death Valley. So he’s seen horror-film-quality blisters. Treatment, Vonhof says, is about lancing the blister to release the fluid, then applying antibiotic ointment and medical tape. But what about prevention? “The fit of your shoe; that’s the most important in my view,” says Vonhof. “You’ve got to have room in the toe box, the heel has to hold your foot in there, you don’t want pressure on top of the foot. Plus, you’ve got to keep moisture out.” Ah ha. Moisture. So how do you keep your feet dry when you’re running through rain storms, mud puddles, or sweat-inducing heat? With shoes that stay dry no matter what, that’s how. “Only a good fitting shoe will keep your foot in position inside the footwear and prevent blisters,” says Michael Carli, an Italian-based shoe designer for La Sportiva. “But fit goes hand in hand with appropriate material and technology selection. It’s crucial to keep the foot cool and dry, too. Materials need to be comfortable, quick-drying, breathable, and adapt to the user’s foot.” GORE-TEX SURROUND® product technology, which La Sportiva uses in some of its high-end hiking shoes, increases the breathability of the shoe by placing venting under the foot for the first time since GORE-TEX fabric technology has been used in outdoor footwear. “This increase in breathable surface area contributes greatly to the extended comfort range of GORE-TEX SURROUND® footwear,” Carli adds. The lesson to be learned here: Sure, you can treat blisters, but you’re much better off preventing them from forming in the first place. And one way to do that is by getting yourself the right pair of shoes.