Subungual Hematoma
Medicine for the Outdoors
Medicine for the Outdoors

Dr. Paul Auerbach is the world's leading outdoor health expert. His blog offers tips on outdoor safety and advice on how to handle wilderness emergencies.

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Subungual Hematoma

The following is a message that I received from a reader:

"Professor Auerbach - I am an avid reader of your blog 'Medicine for the Outdoors.' Your two posts about foot blisters are really interesting. In my hiking experience there is another foot related issue, that is the subungual hematoma in the toenail. I think it could be an interesting subject in one of your blog posts. Thank you very much for the attention."

Well, it just so happens that I have been a sufferer myself, so I'm happy to write a bit about this. Subungual hematoma refers to blood under a toenail or fingernail. In the fingers, this usually occurs from a blow or pinch, such as catching a finger in a door or striking it with a hammer. In the foot, it is commonly caused by repetitive blows in a confined space, such as hiking in a boot with a toe-box that is too small and/or too stiff. The photo above is my foot after a 10 mile hike over rocky terrain in hiking shoes that didn't fit quite right. They were broken in, but they weren't sufficiently flexible for that type of hike. A couple of hours in, I knew I was in trouble because of the pain, but there was no turning back. No surprise, when I took off my sock, I saw the blue color and knew that eventually that particular toenail was a goner.

What can be done about this condition? When it first happens, applying an ice pack might relieve the pain. Certainly, you should trade out the poorly fitted shoes for ones that provide greater room and comfort. If possible, curtail hiking activities for a day or two, and let the situation settle, or the blood collection might increase.

When a fingertip is smashed between two objects, there is frequently a rapid blue discoloration of the fingernail, which is caused by a collection of blood underneath the nail. Pain from the pressure may be quite severe. If the pain is intolerable, it is necessary to create a small hole in the nail directly over the collection of blood, to allow the blood to drain and thus relieve the pressure. This can be done during the first 24 to 48 hours following the injury by heating a paper clip or similar-diameter metal wire to red-hot temperature in a flame (taking care not to burn your fingers while holding the other end of the wire; use a needle-nose pliers, if available) and quickly pressing it through the nail. Another technique is to drill a small hole in the nail by twirling a scalpel blade, sharp knife, or needle. As soon as the nail is penetrated, blood will spurt out, and the pain will be considerably lessened. Before and after the procedure, the finger should be washed carefully. If the procedure was not performed under sterile conditions, administer an antibiotic (such as dicloxacillin, erythromycin or cephalexin) for 3 days.

In the case of my toe (above), the pain subsided with a day's rest from hiking, so there was no benefit to be obtained by draining the blood. A new nail grew in underneath the one shown in the picture, with the entire process taking a full nine months from injury to nail replacement.

Preview the Annual Meeting of the Wilderness Medical Society, which will be held in Snowmass, Colorado July 24-29, 2009.

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Dr. Paul S. Auerbach is the world’s leading authority on wilderness medicine.