Have you ever noticed a black or dark line, spot, or patch appearing on one of your nails and wondered what caused it? A change in nail colour can happen for several reasons, and while some causes are harmless, others may need medical attention. It is important not to automatically assume that a dark nail is simply dirt or a minor injury. Here are four possible reasons your nails may turn black.
1. An injury or repeated pressure
A black nail can develop after you injure your finger or toe, even if the injury seemed minor at the time. Blood can collect underneath the nail after a heavy object hits it, you slam your finger against something, or your shoes repeatedly put pressure on your toenails. This can create a dark red, purple, brown, or black area beneath the nail. As the nail grows, the discoloured area will usually move toward the tip.
2. Fungal infection
Although fungal nail infections are more commonly associated with yellow, white, or thickened nails, some infections can cause darker discolouration. The nail may also become thicker, brittle, crumbly, or develop an unusual shape. Fungal infections are more common in toenails and can gradually spread to other nails if left untreated.
3. Certain medications or medical conditions
Some medications and health conditions can cause changes in nail colour. In some cases, increased production of melanin can lead to dark bands or pigmentation in the nails. This can occur for several reasons, including hormonal changes, certain medications, or underlying medical conditions. If the change appears without an obvious explanation, it is worth having it checked.
4. Melanoma under the nail
A dark streak or patch under a nail can rarely be caused by melanoma, a type of skin cancer. One warning sign is a new dark band that gradually becomes wider or changes in appearance, especially when the pigmentation extends onto the surrounding skin. Although nail melanoma is uncommon, unexplained or changing dark pigmentation should not be ignored.