A black dot on a nail can raise questions about its origin. Discolorations underneath the nail surface can arise from various sources, ranging from minor occurrences to conditions warranting professional medical review. Understanding the potential causes helps distinguish between harmless and concerning situations.
Common Reasons for Discoloration
A frequent cause of dark spots under a nail is a subungual hematoma, resulting from trauma or impact. This injury ruptures small blood vessels beneath the nail plate, leading to blood pooling and appearing as black or dark purple. The discoloration typically grows out with the nail, eventually disappearing as it’s trimmed.
Small foreign objects or splinters can lodge under the nail, appearing as a dark line or dot. These can be tiny pieces of wood, dirt, or other debris. While often harmless, if not removed, they may cause localized discomfort or potential infection.
The nail matrix, where nail growth originates, can develop benign moles, similar to moles found on the skin. A mole in the nail matrix produces pigment appearing as a dark streak running lengthwise along the nail, known as longitudinal melanonychia. These streaks are typically uniform in color and width, growing out with the nail.
Less commonly, fungal infections can lead to nail discoloration, though they usually do not result in a purely black appearance. Severe or chronic infections might cause the nail to become thickened, brittle, and discolored, often appearing dark brown, green, or yellowish. This discoloration occurs as the fungus grows and produces pigments.
Recognizing Subungual Melanoma
A more serious, though less common, cause of a black mark on a nail is subungual melanoma, a type of skin cancer originating in the nail matrix. This rare but aggressive melanoma requires prompt identification and treatment. Unlike benign conditions, it often presents specific differentiating characteristics.
Indicators of subungual melanoma include a dark band or streak wider than 3 millimeters, particularly if its borders are irregular or blurred. This band might also show color variations, appearing darker in some areas.
Concerning changes in an existing nail band include rapid growth in width or darkening of the pigment. The digit involved can be a clue, as subungual melanoma is most frequently observed on the thumb or great toe. This discoloration often appears without prior trauma.
A warning sign is the extension of pigment from the nail plate onto surrounding skin, such as the cuticle or lateral nail folds. This spreading, known as Hutchinson’s sign, indicates abnormal cells moving beyond the nail unit. Additionally, a family history of melanoma or failure of conservative treatments warrant further investigation.
When to Seek Medical Advice
Any new black streak or dot on a nail without a clear history of trauma should prompt a visit to a healthcare professional. While many discolorations are benign, a medical evaluation can help determine the exact cause. Early assessment is important, especially when the cause is uncertain.
If an existing dark streak on a nail begins to change in size, shape, or color, or if its borders become irregular, seek medical opinion. These changes could indicate a progression of a benign condition or a more serious underlying issue. Monitoring these characteristics helps identify potential concerns.
The appearance of Hutchinson’s sign, where pigment spreads from under the nail onto surrounding skin, necessitates immediate medical attention. This can indicate subungual melanoma, and prompt evaluation allows for timely diagnosis and management.
Additional symptoms such as bleeding, pain, or noticeable changes in the nail’s texture or integrity accompanying a dark spot also warrant professional medical advice. These symptoms can be associated with various nail conditions, and a healthcare provider can assess their significance. When in doubt, consulting a doctor is a sensible step to ensure proper care.