A black discoloration under a toenail can be a concerning observation. This common phenomenon has a range of potential causes, varying from minor issues that resolve on their own to more serious conditions that warrant professional medical attention.
Reasons for Toenail Discoloration
One of the most frequent causes of a black toenail is a subungual hematoma, a bruise under the nail. This occurs when small blood vessels beneath the nail plate rupture, causing bleeding and dark discoloration. Such trauma can result from a direct impact, like dropping a heavy object on the foot, or from repetitive stress caused by ill-fitting shoes during activities such as running or hiking. The blood pools under the nail and typically grows out as the nail plate extends over several months.
Fungal infections, or onychomycosis, can also lead to toenail discoloration, which can appear dark brown or black. These infections are caused by dermatophytes, yeasts, or molds that thrive in warm, moist environments. A fungal infection might cause the nail to thicken, become brittle, or crumble at the edges. The affected nail may also lift from the nail bed, creating space for debris to accumulate.
Less commonly, certain bacterial infections can cause discoloration under the nail, typically a greenish-black hue rather than a true black. These infections often occur with other nail issues, such as a lifted nail plate or trauma. Some medications can also induce nail discoloration as a side effect. Certain antibiotics, chemotherapy drugs, and antimalarial medications are known to cause changes in nail color.
A rare but serious cause for a dark streak or patch under the nail is subungual melanoma, a type of skin cancer. This form often appears as a dark, widening band that may extend from the nail bed to the cuticle, a sign known as Hutchinson’s sign. Unlike a bruise, a melanoma streak typically does not grow out with the nail and may change in appearance over time. Any new or changing dark streak under a toenail warrants immediate medical evaluation.
When to Seek Medical Advice
If a black toenail appears without any known trauma, or if the discoloration does not seem to be growing out with the nail, seek medical attention. A persistent or worsening dark spot that remains unchanged for several months may indicate an underlying issue beyond a simple bruise. Any increase in the size or intensity of the black area also warrants a visit.
The presence of pain, swelling, or pus accompanying the discoloration suggests a possible infection or significant trauma. These symptoms indicate inflammation or bacterial involvement beneath the nail. Changes in the nail’s shape or texture, such as thickening, crumbling, or lifting from the nail bed, especially if not associated with a clear injury, should be assessed by a doctor.
A dark streak that extends from under the nail to the cuticle or surrounding skin, known as Hutchinson’s sign, is a significant warning sign for potential subungual melanoma, necessitating urgent medical consultation. Individuals with underlying health conditions, such as diabetes or a compromised immune system, should also consult a doctor for any toenail discoloration. These conditions can increase the risk of complications from minor injuries or infections.
Managing and Preventing Black Toenails
For a black toenail caused by trauma, basic home care can alleviate discomfort. Applying ice to the affected area for 15-20 minutes several times a day reduces swelling and pain. Elevating the foot above heart level minimizes blood pooling under the nail. Over-the-counter pain relievers manage discomfort, and the discoloration will gradually resolve as the nail grows out, which can take several months.
Maintaining good foot hygiene is important in preventing various toenail issues. This involves regularly washing feet with soap and water, ensuring they are thoroughly dried, especially between the toes. Trimming toenails straight across and not too short can prevent ingrown nails and reduce the risk of trauma. Properly trimmed nails are less likely to experience pressure from footwear.
Choosing appropriate footwear is important for preventing black toenails, particularly for those engaged in physical activities. Shoes should fit well, providing enough room in the toe box to prevent toes from pressing against the front of the shoe during movement. Breathable materials in shoes and moisture-wicking socks can help keep feet dry, creating an environment less conducive to fungal growth by pulling moisture away from the skin.
In cases where home care is insufficient or the cause of the black toenail is uncertain, professional treatment may be necessary. A doctor might drain a subungual hematoma if the pressure causes significant pain, or they may prescribe antifungal medications for confirmed fungal infections. If melanoma is suspected, a biopsy of the nail bed will be performed for accurate diagnosis and treatment guidance.