What should you know about dark spots on toenails?

A bruise beneath the nail may appear after tight shoes, stubbing, or repetitive pressure and should gradually move toward the tip as the nail grows. A fungal nail problem more often causes thickening, crumbling, discoloration, or debris. Pigment can also appear as a brown or black band or patch. A photograph and its position, shape, and change over time help a clinician judge whether the colour is in the nail, under it, or on nearby skin.

Keep the nail clean and dry, choose footwear with room for the toes, and avoid scraping, drilling, or applying unlabelled lightening products. Photograph the mark beside a ruler and note tenderness, injury, and whether it moves as the nail grows. Do not cover a changing mark with polish before assessment. A clinician can examine the nail and decide whether testing or treatment is needed. For related skin pigmentation, see Dark Patches On Skin.

Arrange prompt medical assessment if the mark is spreading, irregular, very dark, painful without a clear injury, bleeding, or associated with a swollen or damaged nail fold. Seek urgent care for severe pain after a crush injury, marked swelling, loss of sensation, or a toe that looks pale or blue. A spot that does not grow out with the nail also deserves review.

Ask whether the colour is within the nail plate or beneath it, whether its pattern fits an old injury or infection, and whether a nail sample or specialist examination is appropriate. Mention new medicines, repeated footwear pressure, skin pigment changes, and any family history of nail or skin disease.