Black Toenail in 2026: Causes, Treatment & Prevention — From Trauma to Fungus, What Your Dark Nail Is Trying to Tell You

Acute trauma — stubbing your toe, dropping something heavy on it, or slamming it into a door frame — causes bleeding under the nail. The blood pools and oxidizes, turning dark red, purple, or black within 24–48 hours. Repetitive micro-trauma (like your toe repeatedly jamming into the front of your running shoe) can also cause a black toenail without a single memorable injury event. This is extremely common in runners, hikers, and soccer players.

Pain and throbbing are typical in the first few days, especially if there’s significant blood accumulation. The nail may eventually loosen and fall off — but a new nail will grow in its place over 6–12 months.

Fungal infections of the nail typically start as a white or yellow spot under the nail tip. As the fungus deepens, the nail can thicken, crumble, and darken to brown or black. Unlike traumatic black toenail, fungal discolouration develops slowly over weeks or months and is usually painless unless the nail becomes ingrown or secondary infection sets in.

Fungal black toenail is more common in older adults, people with diabetes, and those who frequently wear closed-toe shoes or use communal showers (gyms, pools). It requires antifungal treatment — topical or oral — and can take months to resolve.

Sometimes a black or dark brown streak on the nail — called a longitudinal melanonychia — is simply a benign pigmented lesion, similar to a freckle on the skin. These are more common in people with darker skin tones and usually appear as a single, vertical band of pigment running from the cuticle to the nail tip.

While most are harmless, any new or changing pigmentation on a single nail should be evaluated by a dermatologist to rule out subungual melanoma (a rare but serious form of skin cancer under the nail).

Certain medications — including some antimalarials, chemotherapy drugs, and oral retinoids — can cause nail discolouration that appears black or dark brown. Systemic conditions like psoriasis, diabetes, or chronic kidney disease can also affect nail pigmentation. If you have multiple nails changing colour simultaneously and no history of trauma, a systemic cause is more likely.

Always mention any new medications or health conditions to your doctor when discussing nail changes.

If the cause is trauma, the black discolouration will grow out with the nail. Fingernails grow faster than toenails (about 3–4 months vs. 12–18 months for a full replacement). The black spot will move toward the tip over time. If the entire nail falls off, a new nail typically covers the nail bed within 8–12 months. Fungal infections can take 6–12 months of consistent treatment to resolve.

Yes, as long as the pain is manageable and there are no signs of infection. If running causes discomfort, try protecting the toe with a silicone toe cap or gel pad. Check your shoe fit — if your toes are hitting the front, consider a larger size or a different lacing technique. If the nail is loose, keep it covered with a bandage to prevent snagging. Stop and consult a doctor if pain worsens or the area becomes red and swollen.

No. While you may see videos online of people doing this, piercing the nail at home carries a high risk of introducing bacteria and causing a serious infection. If the pressure is severe and the injury is recent (within 24–48 hours), a healthcare professional can perform a sterile trephination — a tiny hole in the nail to drain the blood. This is safe and provides immediate relief. Do not use a heated paperclip, needle, or any other DIY method.

In the vast majority of trauma cases, yes — the new nail will grow back completely normal. Sometimes the new nail may be slightly thicker or have a mild ridge, but this usually improves with subsequent nail cycles. If the nail bed was damaged (crushed or cut), there may be permanent thickening or a slight curve. Fungal infections can cause permanent nail distortion if left untreated for a long time.

Rarely — but yes. Subungual melanoma (melanoma under the nail) accounts for less than 1% of all melanomas. Warning signs include: a single dark band on one nail that starts at the cuticle, pigment that spills onto the surrounding skin (Hutchinson’s sign), or a nail that lifts and has a dark growth underneath. If you notice any of these, see a dermatologist promptly. When caught early, subungual melanoma is highly treatable. When in doubt, get it checked out.