Black Spots on Toenails: Causes and Concerns - Dermatology

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Understanding black spots on toenails can be concerning, especially when they appear suddenly and without an obvious cause. Based on your description, there are several potential causes for the black discoloration on your toenail, and it’s essential to consider each one carefully.

1. Subungual Hematoma: One of the most common causes of black spots under the toenail is a subungual hematoma, which occurs when blood collects under the nail due to trauma. This could happen from stubbing your toe or wearing tight shoes. If the discoloration is accompanied by pain or if the nail is lifting, this could be the cause.

2. Fungal Infection: Given your history of athlete's foot (tinea pedis), it’s possible that a fungal infection could be affecting your toenail. Fungal infections can cause discoloration, thickening, and sometimes crumbling of the nail. However, fungal infections typically present with a more yellowish or brownish color rather than a pure black.

3. Melanonychia: This term refers to a brown or black pigmentation of the nail, which can be benign or a sign of more serious conditions like melanoma. Melanonychia can occur due to various reasons, including trauma, systemic diseases, or even certain medications. If the black spot is growing or changing in appearance, it is crucial to have it evaluated by a healthcare professional.

4. Nail Psoriasis: Psoriasis can affect the nails, leading to pitting, discoloration, and sometimes the appearance of black spots. If you have a history of psoriasis or other skin conditions, this could be a potential cause.

5. Other Conditions: Other less common causes include benign tumors, such as a keratoacanthoma, or more serious conditions like melanoma. Melanoma under the nail (subungual melanoma) is rare but can be life-threatening if not diagnosed early. It typically presents as a dark streak that may widen or change in color.

Given that you have not experienced this type of discoloration before and considering your concerns about serious conditions like melanoma, it is advisable to seek a professional evaluation. A dermatologist or a podiatrist can perform a thorough examination, possibly including a biopsy if necessary, to determine the exact cause of the discoloration.

In the meantime, avoid applying nail polish over the affected area, as this can obscure any changes and make it harder for a healthcare provider to assess the condition. Also, keep the area clean and dry, especially if you are dealing with a fungal infection.

In summary, while there are several benign explanations for the black spots on your toenail, it is essential to rule out more serious conditions. Prompt evaluation by a healthcare professional will provide you with peace of mind and appropriate treatment if needed.