Discovering a black toenail can be alarming. Often, the culprit is a simple injury leading to bruising, medically known as a subungual hematoma. However, a black toenail can also signal other underlying issues such as a fungal infection, nutritional deficiencies, or even systemic health conditions like diabetes or cancer. While many black toenails are benign and resolve naturally, some can be painful and require medical intervention. This comprehensive guide will explore the various reasons why has your toenail gone black, delving into the symptoms, causes, treatment options, and preventative measures to ensure your feet stay healthy.
Black Toenail Symptoms
The most prominent symptom of a black toenail is, unsurprisingly, the discoloration itself. This isn’t always a true black; it can manifest as a spectrum of dark shades including reddish, purplish, or brownish. This color change is typically due to blood accumulation beneath the nail. Alongside discoloration, you might experience other toenail symptoms, including:
- Nail pain: Tenderness or throbbing sensations in the affected toe.
- Nail separation: Over time, the toenail may begin to detach from the nail bed.
- Thickening and splitting of the nail: The nail may become abnormally thick or prone to splitting and cracking.
In cases where the area becomes infected, additional symptoms may arise:
- Swelling: Inflammation around the toenail and surrounding skin.
- Odor: An unpleasant smell emanating from the affected toenail.
- Redness: Increased redness and inflammation of the skin around the nail.
- Discharge: Pus or fluid draining from under or around the toenail.
Some nail discolorations appear as linear streaks, known as striations or splinter hemorrhages. These are typically vertical lines within the nail, caused by bleeding from tiny capillaries beneath the nail plate. It’s important to note that any toenail discoloration accompanied by pain or that persists without improvement should be evaluated by a healthcare professional.
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Common Causes of a Black Toenail
Several factors can contribute to toenail discoloration. The most frequent reasons for why your toenail has turned black include:
- Bruising under the nail due to injury or pressure
- Fungal nail infection
- Ingrown toenail
- Underlying health condition
- Melanoma
- Medications
Bruise Under the Nail Due to Trauma or Pressure
Trauma leading to a subungual hematoma is the most prevalent cause of a black toenail. This type of injury can occur from stubbing your toe forcefully or dropping a heavy object on your foot. The impact ruptures small blood vessels, causing bleeding that becomes trapped under the toenail. As the blood accumulates, it darkens, resulting in the characteristic black appearance. In some cases, a black toenail caused by trauma may eventually fall off, typically a few weeks after its appearance. Full regrowth of the toenail can take up to six months.
What Is Runner’s Toe?
Runners and individuals who engage in frequent walking are particularly susceptible to “runner’s toe,” a specific type of subungual hematoma. This condition arises from the repetitive impact of the toe against the inside of the shoe during physical activity. The constant momentum causes the toe to bump or rub against the shoe’s interior, leading to trauma. Furthermore, feet can swell during exercise, exacerbating the pressure within the shoe. Runner’s toe commonly affects the second or third toes, which are often longer and more prone to friction.
Shoes that are too tight or poorly fitted can also contribute to trauma. They may compress the toes, directly damaging the nail, or allow the foot to slide forward with each step, causing repetitive micro-trauma and subungual hematoma.
Fungal Nail Infection
Fungal nail infections, also known as onychomycosis, are frequently caused by dermatophytes, a type of fungal organism. These infections can take hold when there is a break in the skin, such as a cut or crack near the nail, providing an entry point for the fungus. Damp, sweaty feet create an ideal environment for fungal growth. Certain factors increase susceptibility to toenail fungus, including diabetes, vascular disease, and a weakened immune system. While fungal infections more commonly cause yellowing and thickening of the nails, they can sometimes lead to a darker, almost black discoloration in advanced stages or due to specific types of fungi.
Ingrown Toenail
An ingrown toenail occurs when the edge of the toenail grows into the surrounding skin of the nail bed. This condition can lead to bacterial infection as the skin is broken and vulnerable. The resulting infection can contribute to discoloration of the nail, sometimes appearing darker, though often more yellow or brown initially.
Underlying Health Condition
Various underlying health conditions that affect circulation can manifest as changes in toenail color. Conditions like diabetes, kidney disease, heart infections, psoriasis, and anemia can all potentially cause toenail discoloration. In individuals with diabetes, toenail discoloration is often characterized by a yellowish hue, but blackening can occur in certain instances, especially if there is associated trauma or infection. A vitamin B12 deficiency is another health issue that can, in some cases, lead to black toenails. Fortunately, discoloration due to vitamin deficiency is often reversible with treatment.
Melanoma
In rare instances, a black toenail can be a sign of melanoma, a serious form of skin cancer. Subungual melanoma, specifically, is a type of melanoma that develops in the nail bed. When melanoma affects the toenail, it typically appears as a dark streak running lengthwise along the nail. While subungual melanoma is rare, it is crucial to consider this possibility, particularly if the discoloration is a dark streak, is growing, or is not associated with any injury. Early detection and treatment of melanoma are vital.
Medications
Certain medications can also induce toenail discoloration as a side effect. These medications may affect the nail bed, alter blood supply to the nail, or increase the skin’s sensitivity to light. Medications known to potentially cause toenail discoloration include:
- Cancer drugs: Such as tyrosine kinase inhibitors and taxanes.
- Antibiotics: Including tetracycline and zidovudine (used to treat HIV).
- Retinoids: Vitamin A derivatives used in skincare.
- Psoralens: Light-sensitive drugs used for skin conditions like psoriasis.
- Plaquenil (hydroxychloroquine): An antimalarial drug also used for autoimmune conditions.
When to See a Healthcare Provider
If you are aware of a recent injury to your toenail, the discoloration is not painful, and less than half of the toenail is black, it is generally safe to monitor it at home. However, it’s important to seek medical advice if any of the following apply:
- The toenail is painful: Pain that is persistent or worsening is a cause for concern.
- The discoloration appeared gradually: A slow onset of discoloration without a known injury may indicate an underlying issue.
- More than half of the toenail is black: Extensive discoloration, even after trauma, warrants medical evaluation.
- The discoloration has spread outside the nail: Pigment spreading to the skin around the nail could be a sign of melanoma or infection.
- You notice bumps under the nail: Growths or bumps beneath the nail should be examined.
- You have a health condition such as diabetes or vascular disease: These conditions increase the risk of complications and require prompt attention to foot problems.
If you observe discoloration spreading beyond the nail or bumps under the nail, immediate consultation with a healthcare provider is crucial to rule out infection or, in rare cases, skin cancer requiring timely treatment. You can consult your primary care physician or directly seek evaluation from a dermatologist, especially if you suspect melanoma.
Complications
Potential complications from a black toenail can arise if the underlying cause is not addressed or if the condition worsens. These complications may include:
- Permanent nail damage: In some instances, trauma or infection can lead to permanent damage to the nail matrix, resulting in a misshapen or thickened nail regrowth.
- Spread of fungal infection: Untreated toenail fungus can spread to other toes or even fingernails.
- Melanoma spread: If the black toenail is due to melanoma and left untreated, the cancer can spread to other parts of the body, becoming life-threatening.
How Are Black Toenails Diagnosed?
To diagnose the cause of a black toenail, a healthcare provider will begin with a physical examination of the affected toenail. They will inquire about any recent injuries, your activity levels, and your usual footwear. Depending on your symptoms and medical history, they may order further tests to investigate potential underlying conditions contributing to the discoloration.
If a fungal infection is suspected, the healthcare provider may take a small sample of nail clippings for laboratory analysis. This analysis helps identify the specific type of fungus and guide appropriate treatment options.
How Do You Treat a Toenail That Has Turned Black?
Treatment for a black toenail depends largely on the underlying cause. If the black toenail is painless and less than half of the nail is discolored due to a known injury, often no specific treatment is needed. As the nail grows, the discoloration will naturally resolve. However, if more than half the nail is black due to trauma, medical evaluation is recommended to check for a subungual laceration (tear or cut under the nail).
For painful black toenails caused by swelling or pressure from a subungual hematoma, home treatments can provide relief:
- Elevating your foot: Reduces swelling and pressure.
- Applying a cool compress: Helps to reduce pain and inflammation.
A healthcare provider can also treat a painful black toenail due to trauma by performing nail trephination. This procedure involves creating small holes in the nail to relieve pressure and drain the trapped blood. This is most effective if done within two days of the injury. The procedure is generally painless as the toenail itself lacks nerve endings.
In cases of severe trauma, significant nail separation, or extensive discoloration, healthcare providers may recommend nail removal. This procedure is performed after numbing the area to ensure it is pain-free.
If a fungal infection is the cause of the black toenail, treatment options include both topical and oral antifungal medications. Over-the-counter (OTC) antifungal remedies, such as ointments and soaks, are available, but prescription-strength topical and oral medications are often more effective for nail infections. Prescription topical treatments include ciclopirox, efinaconazole, and tavaborole. Oral prescription antifungals include fluconazole, griseofulvin, itraconazole, and terbinafine. Treatment for fungal infections is often prolonged, requiring months or even over a year for complete eradication as the healthy nail gradually replaces the infected portion. The nail may sometimes grow back with a slightly altered appearance.
If the black toenail is due to a bacterial or yeast infection, appropriate treatment, such as antibiotic or antifungal ointments or oral medications, will be prescribed by your healthcare provider.
In the rare event that a black toenail is diagnosed as subungual melanoma, the primary treatment is surgical removal of the cancerous growth. If the melanoma has spread beyond the nail or toe, further treatment options will be discussed with your healthcare provider.
Prevention
While not all causes of black toenails are preventable, particularly sudden injuries, there are steps you can take to minimize your risk:
- Wear properly fitting shoes: Ensure shoes have adequate toe box space to prevent pressure and friction.
- Keep your toes dry and clean: Practice good foot hygiene to prevent fungal infections.
- Avoid wearing open-toed sandals in risky environments: Protect your toes from injury, especially in work or outdoor settings where stubbing or impact is possible.
- Protect your feet from sun exposure: Limit prolonged sun exposure to your feet.
- Apply sunscreen to your feet: When using sunscreen, include your toes to protect against sun damage, especially important in melanoma prevention.
- Trim toenails straight across: Proper toenail trimming helps prevent ingrown toenails.
- Manage underlying conditions: If you have diabetes or other health conditions, ensure they are well-managed to reduce the risk of foot complications.
Summary
A black toenail is often a result of trauma, leading to blood pooling under the nail. In many cases, it resolves on its own as the nail grows out. However, various other factors can cause a black toenail, including fungal infections, ingrown toenails, vitamin B12 deficiency, certain medications, and, rarely, melanoma.
If you are concerned about why your toenail has gone black, and especially if you experience pain, notice gradual discoloration, or observe spreading discoloration, seeking medical advice is essential. Early diagnosis and appropriate treatment can address underlying issues, prevent complications, and ensure the health of your feet.
