Black Toenail Fungus
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What is black toenail fungus?
If you have a dark, thick toenail, it could be toenail fungus, which is usually caused by a type of fungus called dermatophytes. It affects the toenail and the area beneath the nail and causes color changes, thickening, and abnormally shaped nails.
It’s fairly common, with at least 12% of American adults diagnosed with it, according to Seminars in Cutaneous Medicine and Surgery. Older adults and people with diabetes, circulation problems, or a weakened immune system are more likely to have toenail fungus.
This infection doesn’t usually go away on its own, and it can take a year or more to treat it with prescription medications. These are applied to the nail or taken in pill form.
Signs of a toenail fungal infection
- Discolored toenails. Nails can be brown, black, white, or yellow. Usually a small area changes color at first and it slowly spreads.
- Thickened toenails. Over time, the nail becomes thick, material builds up under the nail, and the nail can develop an irregular shape, grooves, or a crumbling appearance.
- Affects one or more toenails. The fungus may spread to other toenails. The big toe is most commonly affected. The fungus can also occur in fingernails.
- Starts at the end or side of the toenail. The infection gradually spreads toward the cuticle.
- Usually painless unless there are skin changes or injury to the nail bed or if shoes press on the thick nail.
- Athlete’s foot. Some people will also have skin fungus on their feet, which looks like red, peeling skin between the toes.
Patients may say that they are embarrassed to go to the pool or the beach, or they avoid wearing sandals. They describe their nails as thick, crumbling, and abnormally colored. One patient described their nails as looking like an animal’s horn, which is pretty accurate. But they are so thrilled when they see results from treatment! —Dr. Anne Jacobsen
How fungus forms on toenails
Usually toenail infection develops when the nail or surrounding skin has a small crack or cut and the area is exposed to fungus in the environment.
Warm, moist conditions allow fungus to grow. Walking barefoot in locker rooms or shared showers can increase your risk of coming in contact with fungus. Having sweaty feet or wearing non-breathable shoes can help the fungus take hold and spread.
Diabetes, peripheral vascular disease, and a weak immune system (especially from HIV) can increase risk for toenail fungus.
It’s also more common in older adults. Up to half of adults over the age of 70 may have toenail fungus, according to the Journal of Clinical Pharmacy and Therapeutics. A previous toenail injury, psoriasis, hyperhidrosis, and smoking can also increase risk. Children are rarely affected.
Is it fungus or melanoma?
Melanoma is a form of skin cancer that can develop on the nail bed. It has a dark brown or black color and can be mistaken for toenail fungus or another toenail problem like a bruise. Melanoma is much less common than toenail fungus, but it can be life-threatening if not caught early.
Both toenail fungus and melanoma can appear as a dark stripe on the toenail and may increase in size over time. The toenail can become split and damaged in both conditions.
Toenail fungus is more likely to cause thickening of the toenail and a buildup of material underneath it. Melanoma causes the skin of the nailbed to change color, which does not happen with toenail fungus, but it can be difficult to see.
Because melanoma can be very aggressive, it’s important to have your doctor examine a darkened toenail. Your doctor can confirm the diagnosis of toenail fungus by looking at clippings under a microscope and of melanoma by taking a biopsy.
How to get rid of toenail fungus
All treatments can take up to a year to work, so you need to be consistent and commit to following the treatment plan for the long haul.
These infections are hard to treat because it’s difficult for medications to get into the keratin that makes up nails and the blood vessels don’t connect to the nail. Many people find it hard to continue to use the medications for as long as is needed and may give up after months or even weeks.
Sometimes the nail will start to look better, but the fungus is still there. Your toenail fungus isn’t cured until your doctor can’t detect the fungus in your toenail clippings.
There are a lot of folk remedies and over-the-counter topical treatments, but if you really want to get rid of this infection, you’re probably going to need to take oral medication. —Dr. Jacobsen
Prescription medications are the only effective treatment options for toenail fungus. It’s also important to keep your feet clean and dry. Wear cotton socks and breathable shoes or try to go barefoot if you’re indoors and not likely to injure your feet.
- Terbinafine (Lamisil) or itraconazole (Sporanox). These prescription antifungal pills are the most effective for toenail fungus. You need to take them for 12 weeks, although some people use intermittent (not continuous) or pulsed dosing (taking the medication just one week out of the month, for a few months) as an alternative to daily treatment. These medications can cause interactions with other medications, so your doctor will need to review your other prescriptions. You also need to have blood work to check your liver enzymes both at the beginning of treatment and every 4 to 6 weeks during treatment. People with diabetes or poor circulation are more likely to need longer treatment.
- Fluconazole (Diflucan). The FDA hasn’t approved this antifungal medication to treat toenail fungus, but some studies show it might be effective and your doctor may prescribe it. It doesn’t cause as many side effects as other pills and is more affordable. But more research is needed.
- Ciclopirox (Penlac) nail lacquer. This polish is most likely to help when only a few toenails are infected and before the fungus spreads to the cuticle. You need to use it consistently for up to a year and even then, according to the Cochrane Database of Systematic Reviews, more than half of people using it do not see results. The treatment may be more effective if your doctor removes or clips your toenails or you take it with prescription antifungal pills.
- Nail removal or trimming. Cutting back the thick toenail or even completely removing it can improve the medication’s effect on the fungal infection. Your doctor or podiatrist (foot specialist) should do the cutting in order to prevent injury or a bacterial infection. Doctors will sometimes permanently remove the toenails if the fungus won’t go away or if it comes back repeatedly after treatment.
- Laser treatments. Lasers, which can heat and kill fungus, are an expensive option and there is little evidence they work for treating toenail fungus.
- Photodynamic therapy. Doctors apply light-sensitive medications to the toenails and then expose them to ultraviolet radiation. There aren’t many studies of this treatment for toenail fungus.
Most of these treatments need to be used for months to a full year to successfully treat the fungus. Commit to making this part of your daily routine so that you get a good result—you’ll be thankful that you did the work to cure your toenail fungus. —Dr. Jacobsen
It’s important to keep your feet clean and dry. Wear cotton socks and breathable shoes or even go barefoot if you’re indoors and not likely to injure your feet.
Natural antifungal substances
- Vicks VapoRub. It contains the natural antifungals eucalyptus oil and camphor. Studies are limited but anecdotal evidence suggests that it might be helpful if used for a long time.
- Tea tree oil. Some people believe the antifungal action works on toenails, but there’s not much scientific proof.
- Snakeroot extract. This oil derived from sunflower plants has natural antifungal properties and might be helpful, but again, there’s little real evidence.
Keep in mind that often there isn’t good quality control on oils and extracts. Also, these products can sometimes be very concentrated, which can cause skin irritation or burns.
Ineffective home treatments
- Baking soda. It can soak up extra moisture if you apply it to your feet, but it probably won’t get rid of an existing toenail infection.
- Vinegar and mouthwash. These are known for disinfecting, but neither has shown any effect on toenail fungus.
- Chopped garlic. Some people rub this natural antifungal agent on the toenails, but it can cause skin irritation and hasn’t shown any benefit.
There are just a few over-the-counter options for treating toenail fungus. These products don’t seem to penetrate the keratin of the nail.
- Non-prescription nail polishes.
- Antifungal creams, ointments, and powders for athlete’s foot or ringworm. These products contain clotrimazole or tolnaftate and aren’t effective for toenail fungus. But you can use them alongside other medications if you have both skin and toenail fungus.
Dr. Jacobsen is a board-certified Emergency Medicine physician and writer for Buoy Health. She received her undergraduate degrees in Chemistry and Biology from Macalester College (2006) and graduated from the University of Kansas School of Medicine (2010). She completed an Emergency Medicine residency program at the University of Missouri-Kansas City (2013). She practices community Emergency Medicine in Kansas City and is also engaged in urgent care telemedicine. She joined Buoy Health in 2021. She is passionate about explaining medicine in terms that patients can understand. She hopes to empower her patients with great educational resources so they can understand their current medical concerns and improve their health for the future.