Why does running cause blisters, anyway?
Chances are you’ve had a blister at one point of your life—whether attributed to pounding the pavement or just walking around in too-tight dress shoes for one hour too many—but did you ever wonder what they actually are?
Put simply, “a blister is a raised area of skin filled with clear fluid,” David M. Smith, M.D., a sports medicine physician at the University of Kansas Health System, tells SELF. “They are caused by friction or pressure on the upper layer of skin sliding against a deeper area of skin.”
When you’re running, tight shoes and pressure points from bones on your feet close to the surface of your skin are typically to blame, since they cause repetitive rubbing of these layers of skin, he explains. The body’s response to this is to form a bubble of clear, watery fluid between the layers of your skin to help reduce tissue damage and promote healing.
What should you do when you get a blister?
It’s the fluid trapped within the blister exerting pressure on your skin that leads to the pain you feel, podiatrist Robert Eckles, D.P.M., M.P.H., an associate professor in the department of orthopedics at the New York College of Podiatric Medicine, tells SELF. Which then leads to one of the biggest questions with blisters: to pop or not to pop?
Unfortunately, there’s no clear-cut answer, says Dr. Eckles—there are experts on both sides of the issue. In fact, while the American Academy of Dermatology recommends against popping a blister in most cases to avoid infection, it does also recognize that if the blister is large and very painful, it may be necessary to drain it. (Caveat: If you have diabetes or poor circulation, you should always check with a doctor before self-treating any blister, as it may rapidly progress to infection and ulceration, says Dr. Eckles.)
Dr. Smith—an advocate of not popping—recommends simply applying an extra layer to protect it and prevent painful friction when you run.
“Take some thin moleskin [a padded adhesive available in any drugstore], cut a hole the size of the blister, and apply the moleskin with the blister fitting in the center of the hole,” says Dr. Smith. “This allows the friction and pressure to be transferred more to the moleskin and less to the blister, and may allow a runner to continue training.” If you don’t have moleskin at home, you can apply a light layer of lubricating jelly (like Vaseline or Aquaphor) over the blister, then cover with an adhesive bandage. Replace this frequently to wash the skin and reduce your chance of infection, he says.