Black spot under toenail

by Liz
(Leeds, West Yorkshire, United Kingdom)

Some weeks ago I spotted a black spot under my toenail. First I though it might be a mole, as I am prone to getting new very often. Today I was taking my socks off and noticed that a second one appeared almost next to it. Both spots seem quite symmetric, and I do not have any type of discomfort. Could this be some type of nail infection?

RESPONSE

Hi Liz,

Sitting on the other side of the internet, I cannot pretend to know exactly what those black spots under your toe nail actually are, but I will give you some insight and what you can do about them.

The majority of spots that occur underneath a nail are harmless. In most cases it is dry blood usually from some sort of trauma to the nail bed. The trauma does not have to be as severe as dropping something on your toe or someone stepping on it. In many instances it is from repetitive micro trauma such as wearing a shoe with a narrow toe box thus creating too much pressure on the nail and it starts to bleed underneath. If you happen to be athletic, that too can create this type of micro trauma.

In many instances it can be mild bleeding from an irregularity on the nail bed, again usually from nail irritation.

Another very common cause of discoloration underneath a toe nail can be from fungus. I enlarged your pictures as best I could and it appears that the nail surrounding the two dark spots is discolored, which certainly may be fungus.

The third cause of discoloration under a nail bed is from a growth growing on the nail bed. This can range in most cases from a mole to a granuloma (which is scar tissue from irritation), all the way up to a skin cancer.

So now we know it could be any number of possible conditions, again most of them harmless, but keeping in the back of our mind that there is possibility of a more serious problem.

Here is my recommendation. Do nothing right away. Mark where the discoloration is today, relative to the skin on the side of the nail. Wait two months and see if the discoloration, both of them, grow forward, leaving no residual discoloration in the original spots.

The reason I recommend this is because the majority of harmless discolorations under a nail will grow forward as the nail grows. Eventually the discolorations will be at the end of the nail where it can then be cut away. That's the end of that.

Now, if the discoloration does not grow forward, there is a very good chance that there is a growth on the nail bed. Again, most of these are not serious problems, but at that point I would recommend seeing a doctor to have the nail removed to see what kind of growth may be on the nail bed. If the growth is suspicious it may have to be removed and biopsied. Although not common, skin cancers particularly melanoma can occur underneath a nail and this needs to be ruled out.

If during this two month period the discoloration appears to be getting larger, even if it may appear to be growing forward, that too would be a warning sign that there may be some sort of growth on the nail bed and it should be investigated.

Marc Mitnick DPM
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