A black discoloration on a nail can be concerning, as it may signal various underlying issues. While some causes are harmless, others require prompt medical attention. This discoloration can result from injuries, fungal infections, certain medical conditions, or medications.
Common Reasons for Discoloration
A subungual hematoma, a bruise under the nail, is a frequent cause of black discoloration. This occurs when trauma, such as stubbing a toe or dropping a heavy object, ruptures blood vessels, causing blood to pool. The discoloration can appear red, purple, or dark brown to black, typically resolving as the nail grows out over several months. Minor cases often heal without intervention, but large hematomas may cause pressure and pain, sometimes requiring drainage.
Fungal infections can also cause nails to darken. These infections may present with black, brown, or yellow discoloration, often accompanied by thickening, crumbling, or lifting of the nail plate. Fungi thrive in warm, moist environments, making toenails particularly susceptible. This condition can spread if left untreated, potentially affecting other nails or skin.
External factors can temporarily stain nails black. Substances like dyes, certain medications, tar, or some foods can cause superficial discoloration. This staining will typically fade or grow out as the nail plate is replaced.
Certain medications, such as some antibiotics, antimalarials, and chemotherapy drugs, can cause nail darkening. These drug-induced changes are usually temporary and may resolve once the medication is stopped.
Underlying Health Conditions
Black nail discoloration can sometimes indicate systemic health issues. While less common than fungal infections, certain bacterial infections can cause dark discoloration, often accompanied by pain or pus.
Psoriasis, a chronic autoimmune condition affecting the skin, can also manifest in the nails. Nail psoriasis may cause various changes, including discoloration that can appear black or brown, as well as pitting, ridging, or separation of the nail from the nail bed.
Disorders affecting the body’s hormonal balance can also lead to nail changes. Addison’s disease can cause increased pigmentation in various body parts, including the nails, due to hormonal imbalances, leading to generalized darkening.
Hemochromatosis, an iron overload disorder, can sometimes be associated with nail discoloration. An accumulation of excess iron in the body can lead to various dermatological signs, including changes in nail appearance.
Advanced stages of kidney and liver disease may also be associated with nail discoloration. These conditions affect overall body systems, and nail changes can indicate underlying systemic illness.
Melanoma: A Serious Consideration
Subungual melanoma is a serious cause of black nail discoloration, a skin cancer developing under the nail. It often appears as a dark streak or patch. Unlike a bruise that grows out, melanoma may persist, widen, or change over time, and might not be linked to injury.
The ABCDEF rule helps identify suspicious nail changes:
- A: Age (peaks in 5th-7th decades, more common in African Americans and Asians).
- B: Band of brown or black color (irregular borders).
- C: Change in band’s size, shape, or color, or lack of improvement.
- D: Digit involved (thumb or big toe more common).
- E: Extension of pigment onto the nail fold (Hutchinson’s sign).
- F: Family or personal history of melanoma.
Any dark streak under the nail displaying these characteristics warrants immediate medical evaluation.
When to Consult a Doctor
Consult a healthcare professional for black nail discoloration if it persists or worsens, especially without a clear traumatic injury. Medical attention is also warranted if the cause is not obvious, such as no recent injury or exposure to staining substances.
Signs of infection, such as increasing pain, swelling, or pus, require medical intervention. Changes in nail shape or texture, including thickening, brittleness, or separation from the nail bed, also warrant review. If black pigment spreads onto the surrounding skin (Hutchinson’s sign), immediate evaluation for potential melanoma is crucial. Multiple black nails may suggest a systemic issue.
Diagnostic Approaches and Management
When evaluating black nail discoloration, a doctor will typically begin by taking a detailed medical history, asking about symptoms, recent injuries, medications, and general health. This is followed by a thorough physical examination of the affected nail and surrounding areas.
To establish a definitive diagnosis, several tests may be performed. A nail clipping or scraping might be taken for microscopic examination or for fungal culture to identify infections. If melanoma is suspected, a biopsy of the nail matrix or nail bed is necessary for a conclusive diagnosis. Blood tests may also be ordered if an underlying systemic condition is considered a possibility.
Management depends on the underlying cause. Minor subungual hematomas often resolve naturally, but large or painful ones may require drainage. Fungal infections are treated with antifungal medications. For systemic conditions, managing the primary disease is the focus. Melanoma cases usually require surgical removal, and early, accurate diagnosis is crucial for effective treatment.