Why are my toenails dark?

This patient came to see me after noticing their large toenails turning a dark brown color. They remembered wearing uncomfortable shoes, and running before the discoloration on the nails formed. I diagnosed them with a condition called subungual hematoma. This means you have bleeding under a fingernail or toenail. A dark-colored discoloration (red, maroon, or purple-black) under all or part of the affected nail is typically present. You may also notice tenderness and swelling of the tip of the affected finger or toe. It usually happens if the nail gets injured, and blood accumulates under the nail bed. There is typically no pain associated with subungual hematoma, however it can cause intense pain, and throbbing as blood collects under the nail. Unless you also have broken bones or damage to the nail bed and/or surrounding tissues, this injury usually isn’t worrisome.

If you had a severe blow to a finger or toe, either seek immediate medical attention from your doctor, or go to an emergency room. You should do this in case you have broken bones, or serious damage to the nail bed and/or surrounding tissues. You’ll probably also have an X-ray taken to see if you have a bone fracture or other injury. Treating a painless and small subungual hematoma usually is not necessary. If there is pressure generated by pooled blood under the nail, this can be extremely painful. To relieve the pain, your doctor may perform decompression, also called trephination, which allows the underlying blood to drain, relieving pressure and pain to the area.

Your doctor will also examine your nails to make sure what they see is actually blood, and not pigmentation of the nail, called melanonychia. Melanonychia is brown or black discoloration of a nail. It may be diffuse, or take the form of a longitudinal band. Where melanonychia is attributed to a benign cause, no further treatment is necessary. The management of cancerous forms of melanonychia requires complete excision of the tumor, and may require amputation of the digit.

Dr. Cindy N. Berthelot, M.D. is a board certified dermatologist treating patients in the greater Houston community, including Clear Lake, League City, Friendswood, Pasadena, Deer Park, Dickinson, Pearland, Alvin, Seabrook, Kemah, Webster, Galveston, Texas City, La Marque, and Santa Fe, Texas. To make an appointment with Dr. Berthelot, please contact us at 281.480.7272.