A black toenail can be a concerning observation. While often a minor issue, it can sometimes signal a more serious underlying condition. Understanding the various reasons a toenail might turn black helps in determining when medical attention is necessary.
Common Reasons for Black Toenails
Bleeding under the nail, medically termed a subungual hematoma, is a frequent cause of a toenail turning black. This occurs when trauma to the toe, such as stubbing it, dropping a heavy item, or repetitive impact from ill-fitting shoes or activities like running, causes blood vessels beneath the nail to rupture. The trapped blood initially appears dark red or purple, gradually turning black as it dries and clots, causing pressure and pain. This discoloration resolves as the nail grows out, which can take several months.
Fungal infections, known as onychomycosis, can also cause toenail discoloration. This darkening often results from debris accumulating under the nail or pigment production by the fungus itself. A fungal infection might also present with symptoms such as nail thickening, crumbling, distortion, or an unpleasant odor. Fungi thrive in warm, moist environments, making toenails particularly susceptible.
Other Potential Causes
In rare instances, a black toenail can be a manifestation of subungual melanoma, a serious form of skin cancer that develops under the nail. This condition often appears as a dark, irregular streak or patch that may spread to the cuticle or surrounding skin, unlike a bruise which grows out with the nail. Early detection is important for this type of melanoma, which can sometimes be mistaken for a hematoma. A dark streak that increases in size or appears without known injury raises suspicion.
Certain medications can induce nail discoloration. Some chemotherapy drugs, antimalarials, and specific antibiotics may cause such changes. These drug-induced changes can present as transverse or longitudinal bands and resolve after the medication is discontinued.
Some underlying systemic health conditions can also cause changes in nail color. Diseases affecting circulation, such as diabetes, kidney disease, or heart conditions, may lead to nail discoloration. While less common causes for a black toenail, these systemic issues indicate a broader health concern.
When to Consult a Doctor
Seeking medical attention for a black toenail is advisable under several circumstances. If the black discoloration appears without any known trauma or injury, or if it spreads or changes rapidly in appearance, professional evaluation is warranted.
Other indicators include associated pain, swelling, redness, or pus around the nail, which could suggest an infection. If the blackness does not grow out with the nail over time, or if there is a dark streak running the entire length of the nail, especially if it is widening or irregular, medical consultation is recommended. Individuals with a personal or family history of melanoma should also consult a doctor if they notice any unusual nail changes.
What to Expect at the Doctor’s Office
When consulting a doctor for a black toenail, the visit begins with a thorough medical history. The doctor will inquire about recent injuries, current medications, and any other symptoms experienced. A physical examination of the affected nail and surrounding area will follow to assess the discoloration and nail integrity.
To diagnose the cause, the doctor might perform diagnostic tests. A nail clipping may be taken for a fungal culture to check for infection, or, if melanoma is suspected, a biopsy of the nail matrix or nail bed might be performed. Treatment depends on the diagnosis; a minor subungual hematoma might only require observation, while a fungal infection would be treated with antifungal medication. For more serious conditions like melanoma, referral to a specialist would be the next step.