Why is Your Toenail Black?

If you are a long-distance runner, you have likely seen it in the locker room or maybe even on your own feet:

The Black Toenail.

In the running community, it is often worn as a badge of honor—proof that you put in the miles, ran the marathon, and pushed your limits. But medically speaking, that badge is a Subungual Hematoma (bleeding under the nail).

While many runners shrug it off, ignoring a black nail can sometimes lead to permanent nail deformity or infection. Read on for Oak Foot & Ankle’s guide to management, prevention, and treatment of this condition.

Why Does It Happen? (The Micro-Trauma)

Runner’s Toe is caused by repetitive micro-trauma. Every time you take a step, your foot slides forward slightly. If your toenails are too long or your shoe is too tight, the tip of your toe bangs against the front of the shoe.

  • The Math: multiply that tiny impact by 50,000 steps in a marathon.
  • The Result: The delicate skin under the nail bed bleeds. The blood gets trapped between the hard nail plate and the sensitive skin, turning black or purple.

SCENARIO A: Leave It Alone

  • The Pain: It hurt yesterday, but today it’s just a dull ache or painless.
  • The Look: The black spot covers less than 50% of the nail.
  • The Plan: Do nothing. The blood has already clotted. The nail might eventually fall off (don’t rip it!), but a new one will grow in behind it. You can paint over it if the color bothers you.

SCENARIO B: See a Podiatrist (Drain It)

  • The Pain: It is throbbing intensely. You can feel your heartbeat in your toe.
  • The Look: The nail is raised, or the black spot covers the entire nail.
  • The Danger: The trapped blood is creating massive pressure. If not released, it can kill the nail matrix (root), causing the new nail to grow back thickened or deformed forever.
  • The Fix: We use a sterile, heated instrument to bore a tiny hole in the nail plate. The blood drains instantly, the pressure vanishes, and the relief is immediate. (And no, it doesn’t hurt!)

Warning: Do NOT Do “Home Surgery”

We know the “hot paperclip” trick is popular on YouTube. Please don’t do it.

Using a non-sterile paperclip or needle introduces bacteria directly into a bed of blood—a perfect recipe for a bone infection (Osteomyelitis) in the tip of the toe. For those with diabetes, other complications are possible, too.

Prevention: Save Your Nails

You don’t have to lose a toenail to run a marathon.

  1. Size Up: Your running shoes should be a half to a full size larger than your street shoes. Your feet swell when you run; give them room.
  2. The “Thumb” Rule: There should be a thumb’s width of space between your longest toe and the end of the shoe.
  3. Trim Short: Keep toenails cut short and straight across before long runs.
  4. Lacing: Use the “Heel Lock” lacing technique to stop your foot from sliding forward.

Wear your medals, not your injuries. If your toe is throbbing after your latest race, don’t tough it out. Come in for a quick, painless drainage, and get back to training comfortably!

Oak Foot and Ankle in Oak Lawn, IL, provides expert podiatric care for patients of all ages. Specializing in sports medicine, diabetic foot care, and innovative treatments, we help you stay active and comfortable. Need assistance? Contact us today!