A fingernail or toenail can be injured by a blow to the nail or by closing the finger or toe in a door or drawer. This kind of trauma commonly results in blood under the nail, a condition called subungual hematoma. Nails also can be accidentally torn or split, or a splinter can get under the nail.
Repeated trauma to toenails, caused by ill-fitting shoes, can lead to deformities in the nails. The deformities may resemble a fungal infection; nails can be thickened or discolored and can lift away from the nail bed, which causes cosmetic concerns.
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