A toenail appearing black underneath is a common observation that can cause concern. This discoloration often signals an underlying issue, varying from minor conditions that resolve on their own to more significant health problems. Understanding the different reasons behind this change in nail color can help individuals determine when to seek professional medical advice.
Common Reasons for Discoloration
One of the most frequent causes of a black toenail is a subungual hematoma, which is essentially a bruise under the nail. This occurs when trauma, such as stubbing a toe, dropping a heavy object on the foot, or even repetitive pressure from ill-fitting shoes during activities like running, causes blood vessels beneath the nail to break and bleed. The trapped blood appears dark, often purplish-black, and can be accompanied by pain or pressure due to fluid accumulation. The discoloration typically remains as the nail grows out, gradually moving towards the tip until it is completely removed by trimming.
Fungal infections, medically known as onychomycosis, can also lead to toenail discoloration, sometimes appearing black. While these infections often present as white or yellowish changes, debris accumulating under the nail can cause a darker hue. Fungi thrive in warm, moist environments like those found within shoes and socks, making toenails particularly susceptible. Beyond discoloration, fungal infections may also cause the nail to thicken, become brittle, or even separate from the nail bed.
Beyond injury and infection, some individuals experience hyperpigmentation, which refers to harmless changes in pigment that can make the nail appear darker. This can be a natural variation in skin tone, or it can develop over time without any underlying medical concern. This type of discoloration usually presents as a uniform darkening rather than a localized spot or streak.
Serious Underlying Conditions
While less common, a black toenail can occasionally indicate a serious medical condition. Melanoma, a severe form of skin cancer, can manifest as a dark streak or patch under the nail, known as subungual melanoma. This condition is particularly concerning if the dark streak is new, rapidly changing in size or color, or if the pigmentation extends to the skin surrounding the nail, a sign known as Hutchinson’s sign. Unlike a bruise, melanoma under the nail typically does not have a history of trauma and will not grow out with the nail.
Bacterial infections can also cause nail discoloration, sometimes appearing dark. These infections often present with additional symptoms such as pain, swelling, redness around the nail, and sometimes pus formation. They can arise from minor cuts or breaks in the skin around the nail, allowing bacteria to enter and multiply.
Certain medications may induce nail discoloration as a side effect. Some chemotherapy drugs, antimalarial medications, and even some antibiotics can cause darkening or the appearance of dark bands. This discoloration typically affects multiple nails and resolves after the medication is discontinued, though it may take time for the nail to grow out.
When to Consult a Healthcare Professional
It is advisable to consult a healthcare professional if a black toenail does not improve or worsens over time. Persistent discoloration, especially if its cause is uncertain and not linked to a clear injury, warrants medical evaluation.
Seek medical attention if the black toenail is accompanied by:
- Significant pain, swelling, or signs of infection such as redness, warmth, or pus.
- Changes in the nail’s texture, shape, or thickness.
- Discoloration spreading to the surrounding skin, particularly new or changing dark streaks extending to the cuticle.
- Underlying health conditions like diabetes or a weakened immune system, which can complicate nail issues and increase infection risk.
Understanding Diagnosis and Treatment
When visiting a doctor for a black toenail, the diagnostic process typically begins with a thorough physical examination of the affected nail and a review of the patient’s medical history. The doctor will inquire about any recent injuries, the onset and progression of the discoloration, and any other symptoms experienced.
To determine the cause, the doctor might perform specific tests. These include a nail clipping or scraping for a fungal culture if infection is suspected, or a biopsy of the nail matrix or nail bed for suspected melanoma. In cases of severe trauma or suspected fracture, an X-ray of the toe may be ordered.
Treatment approaches vary widely based on the underlying cause.
Subungual Hematoma Treatment
For significant pain or pressure, a procedure called trephination may be performed to drain trapped blood. Small, painless hematomas are observed as the nail grows out.
Fungal Infection Treatment
Fungal infections are typically treated with topical or oral antifungal medications.
Bacterial Infection Treatment
Bacterial infections require oral or topical antibiotics.
Melanoma Treatment
Melanoma often requires surgical removal of the affected nail and surrounding tissue, sometimes followed by further oncological treatments.
Medication-Induced Discoloration Treatment
For medication-induced discoloration, adjusting medication or managing symptoms as the nail grows out may be considered.