Dark toenails are almost always treatable, but the right approach depends entirely on what’s causing the discoloration. A toenail that turned dark after stubbing your toe needs different care than one that slowly changed color over months. The three most common causes are trauma (a bruise under the nail), fungal infection, and medication side effects. Figuring out which one you’re dealing with is the first step toward fixing it.
Identify What’s Causing the Discoloration
A bruise under the nail, called a subungual hematoma, is the most common reason for a suddenly dark toenail. It happens when blood pools between the nail and the nail bed after an injury. That injury can be obvious, like dropping something heavy on your foot, or subtle, like weeks of running in shoes that press against your toenails. The nail typically looks black-and-blue or black-and-purple, feels tender to the touch, and may throb with pain.
Fungal infections develop more gradually. You might notice the nail thickening, becoming brittle, or developing a yellowish-brown to dark discoloration that spreads over time. There’s usually no pain early on, but the nail can become uncomfortable as it thickens and distorts.
Certain medications can also darken nails by activating the pigment-producing cells in the nail matrix. Chemotherapy drugs are the most common culprits. This type of discoloration often shows up as brown-to-black vertical bands running the length of the nail, or as an overall darkening of the entire nail plate. If you started a new medication and noticed nail changes, that connection is worth exploring with your prescriber.
Treating a Bruised Toenail at Home
Most bruised toenails heal on their own without any medical intervention. The discolored nail gradually grows out and is replaced by a healthy one. For a toenail, that process takes anywhere from 6 months to 2 years, with 18 months being a reasonable average. In the meantime, here’s what helps:
- Ice and elevation. In the first 24 to 48 hours after injury, applying ice (wrapped in a cloth) and keeping your foot elevated reduces swelling and pain.
- Warm soaks. After the initial swelling subsides, soaking your foot in warm water with 1 to 2 tablespoons of Epsom salt per quart of water for 15 minutes can relieve discomfort. Dry your foot completely afterward.
- Protect the nail. Wear roomy shoes that don’t press on the injured nail. If the nail feels loose, keep it covered with a bandage to prevent it from catching on socks or bedding.
If the bruise covers more than half the nail and the pain is significant, a doctor can drain the trapped blood through a quick procedure called trephination. This involves making a tiny hole in the nail plate to release the pressure. It’s fast (often less than a second for the actual puncture) and provides almost immediate relief. The catch: it only works within the first one to two days after injury, before the blood clots. After that window, you’re better off letting the nail grow out naturally.
If the nail is cracked, split, or lifting away from the nail bed, simple drainage won’t be enough. Those injuries typically require a doctor to remove the nail so the nail bed underneath can be properly examined and treated.
Treating a Fungal Infection
Fungal toenail infections are stubborn. Over-the-counter antifungal creams designed for athlete’s foot generally don’t penetrate the nail plate well enough to clear an established infection underneath it. Prescription treatments fall into two categories: topical solutions applied directly to the nail, and oral medications taken by mouth.
Oral antifungal medication is the most effective option. It works from the inside out, reaching the infection through your bloodstream. A typical course lasts 12 weeks, though the nail won’t look fully normal until a healthy one grows in to replace it, which again can take over a year. Your doctor will likely run blood tests before and during treatment to monitor liver function, since oral antifungals are processed by the liver.
Prescription topical solutions are an alternative for mild to moderate infections or for people who can’t take oral medication. These are painted onto the nail daily, but the treatment timeline is much longer: 48 weeks for toenails. Cure rates are lower than with oral treatment, but topicals carry fewer systemic side effects.
Whichever route you take, the visible results lag far behind the actual treatment. The medication kills the fungus, but the dark, damaged nail has to physically grow out and be replaced. Don’t judge whether treatment is working based on how the nail looks at week six.
When Dark Toenails Need Urgent Attention
Most dark toenails are harmless, but in rare cases, the discoloration signals subungual melanoma, a form of skin cancer that develops under the nail. The key differences from a bruise are worth knowing.
A bruise under the nail tends to be a uniform dark patch, often with purplish, reddish, or reddish-black tones. It stays the same size or slowly grows out with the nail. Melanoma, on the other hand, almost always appears as dark streaks or bands running lengthwise along the nail. Another red flag is the Hutchinson sign: darkened pigment that extends from the nail onto the surrounding skin of the cuticle or nail fold.
The simplest rule of thumb: if your toenail darkened after a clear injury, it’s very likely a bruise. If a dark band or streak appeared with no obvious cause, isn’t growing out over several months, or is widening over time, get it evaluated by a dermatologist. This is especially important if you have only one affected nail and no history of trauma to it.
Preventing Dark Toenails
Repetitive microtrauma is the most preventable cause of dark toenails, and it’s extremely common among runners, hikers, and anyone who spends long hours on their feet in poorly fitting shoes. Your shoes should leave about half an inch of space between your longest toe and the front of the shoe. You should be able to wiggle all your toes freely. Shoes designed for your specific activity make a real difference, since running shoes, hiking boots, and work boots distribute pressure differently.
For fungal prevention, keep your feet dry. Fungi thrive in warm, moist environments like sweaty shoes and gym showers. Rotate your footwear so each pair has time to dry out between uses, wear moisture-wicking socks, and use shower shoes in public locker rooms. Trimming your nails straight across and keeping them at a moderate length also reduces the chance of nail trauma that can create entry points for fungal organisms.