What Does It Mean When Your Nail Turns Black?

Black nails typically result from blood trapped under the nail (subungual hematoma) or fungal infections. Trauma from dropping objects, stubbing toes, or repetitive pressure creates bleeding beneath the nail plate, causing dark discoloration. Fungal infections can also darken nails, appearing black or dark brown with thickening. Less commonly, black nails indicate melanoma, especially if accompanied by irregular borders or rapid changes. Other causes include certain medications, bacterial infections, or underlying health conditions affecting circulation. If black discoloration appears suddenly without trauma, spreads to surrounding skin, or includes pain and swelling, seek medical evaluation promptly.