Dark toenails can be a cause for concern, stemming from minor issues to more significant underlying health conditions. Understanding the potential reasons behind this discoloration can help determine the appropriate course of action. This article explores common and less common causes of toenail darkening, and provides insight into when professional advice may be beneficial.
Causes from Injury and Trauma
Physical impact is a frequent reason for toenails to turn dark, typically resulting in a subungual hematoma. This occurs when blood vessels beneath the nail plate rupture, causing blood to pool under the nail. Dropping a heavy object or stubbing a toe can easily lead to this injury. The pooled blood appears as a dark spot or bruise, ranging from reddish-purple to black, depending on the severity and age of the injury.
Repetitive trauma, often from ill-fitting footwear or strenuous activities, can also cause toenail darkening. Shoes that are too tight or too loose allow the toes to repeatedly hit the front or top of the shoe, creating micro-traumas. Activities like long-distance running or sports involving sudden stops can subject toenails to constant pressure.
This repetitive stress can lead to bleeding under the nail, causing dark spots or a uniformly darkened nail. The nail may also thicken or lift. The dark discoloration from trauma usually grows out with the nail over several months as the nail plate gradually replaces itself.
Fungal and Other Infections
Fungal infections, medically known as onychomycosis, are a common cause of toenail discoloration. These infections typically begin as a white or yellow spot under the nail tip, but as the fungus spreads, the nail can turn yellow, brown, or black. The discoloration is usually accompanied by other changes, such as thickening, brittleness, or crumbling at the edge. The nail may also become distorted in shape and emit a foul odor.
Fungi thrive in warm, moist environments, making feet susceptible to infection, especially within shoes. Less common bacterial infections can also cause nail discoloration, sometimes leading to a green or black hue. For instance, Pseudomonas aeruginosa can cause a greenish-black discoloration under the nail, often associated with a distinct odor. These infections typically involve changes in the nail’s texture or separation from the nail bed, in addition to the color change.
Underlying Medical Conditions
Dark toenails can sometimes indicate more serious underlying medical conditions, though these are less common. Rarely, a dark streak or spot under the toenail can be a sign of subungual melanoma, a serious form of skin cancer. This melanoma often appears as a dark, irregular band extending from the nail base to the tip, potentially involving the surrounding skin. Any suspicious or changing dark marks under the nail should be evaluated by a medical professional.
Certain medications can also cause nail discoloration as a side effect. These include some chemotherapy agents, antimalarial medications, and antibiotics like minocycline. Systemic diseases can also manifest in nail changes, including discoloration or altered growth patterns. Conditions like kidney disease, diabetes, or heart conditions might affect nail health. Some individuals, particularly those with darker skin tones, may naturally develop benign longitudinal melanonychia, which presents as dark, vertical streaks due to increased melanin production in the nail matrix.
When to Seek Professional Advice
Seek medical attention if a dark toenail develops without a clear injury or if the discoloration does not improve. Persistent pain, swelling, or redness around the nail warrant professional evaluation. If a dark spot or streak appears to be growing, changing rapidly in size or shape, or extending onto the surrounding skin, consult a doctor. This is crucial if melanoma is a concern, as early diagnosis is important for this condition.
A visit to a doctor or podiatrist is also recommended if the nail becomes detached from the nail bed or undergoes significant changes in texture or thickness. Individuals with underlying health conditions, such as diabetes or circulatory problems, should be vigilant about any changes in their toenails. These conditions can impair healing and increase the risk of complications from even minor nail issues.