The most common cause for black toenails is trauma. Any time the nail is stomped on, dropped on, or banged against something (a soccer ball, a table or chair leg, or even the fronts of your shoes), you risk damage that could result in a subungual hematoma. That’s the medical term for blood from an injury that pools under the nail.
The pooled blood doesn’t stay fresh, but turns darker and thickens. This discolors the nail, but also puts pressure on the tissues around it, because the blood has nowhere to go. The toe can become painful, and foul odor or a discharge can occur.
There are a couple of other instances where your toenail could turn color: a fungal infection that degrades the nail keratin, or malignant melanoma, a dangerous but rare form of cancer. You should always get a medical diagnosis for what’s causing your discolored nails, to rule out other such things, as well as fractures or damage to the nail bed. For an assessment, or for ideas on how to treat black toenails, call Rocky Mountain Foot & Ankle Center in Colorado. You can reach all four of our Denver area offices at (303) 423-2520.