A black or darkened toenail can look alarming, but it’s not always serious. Sometimes it’s just a minor injury—other times it may point to something that needs attention.
🩸 1. Bruising (Most Common Cause)
Known as a subungual hematoma, this happens when blood collects under the nail after:
Dropping something on your toe
Tight shoes causing repeated pressure
Sports injuries
👉 Usually harmless and grows out with the nail.
🍄 2. Fungal nail infection
A fungal infection can cause nails to become:
Dark, thick, or brittle
Discolored (yellow, brown, or black in some cases)
👉 Needs treatment if it spreads or worsens.
🦠 3. Bacterial Infection
Certain bacteria can cause dark green or black discoloration, often with:
Bad odor
Soft or damaged nail
⚠️ 4. Melanoma (Rare but Serious)
In rare cases, a dark streak or spot under the nail could be a form of skin cancer.
🚨 Warning signs include:
Dark line that doesn’t grow out
Pigment spreading to surrounding skin
No history of injury
Nail becoming distorted
👉 This requires immediate medical evaluation.
🧦 5. Repeated Trauma
Runners or athletes may develop black toenails from constant pressure (“runner’s toe”).
⏳ When Should You Worry?
Seek medical advice if:
The nail is very painful or swollen
The discoloration doesn’t move as the nail grows
You see spreading dark pigment
There’s no clear injury cause
🛑 Final Thought
Most black toenails are harmless and heal over time—but it’s important to watch for unusual signs. When in doubt, getting it checked early can prevent bi.