Is It Toenail Fungus or Something Else?

If you notice an odd spot on your toenail, you might assume it’s a fungal infection. However, there’s a good chance that it’s not.

Spots or discolorations on or under a toenail could be bruises resulting from trauma to the nail, blood blisters, warts, or even subungual melanoma, a type of skin cancer, says Ami Sheth, a doctor of podiatric medicine in Los Gatos, California, and a spokesperson for the American Podiatric Medical Association.

Since nail irregularities can be caused by diseases besides these as well, it’s best to get it looked at, says Dr. Sheth.

Richard Goad, a doctor of podiatric medicine at Baylor Scott & White Health in Waco, Texas, concurs. “Sometimes the nail will be the first place to show another underlying problem,” Dr. Goad says.

So is it a fungus, a false alarm, or another condition entirely?

Types of Toenail Fungal Infections

Toenail infections (onychomycosis) affect about 14 percent of the population at any given time, according to a study published in June 2014 in PloS Pathogens. The most common symptoms of a toenail fungal infection include discoloration of the nail, debris under the nail, irregularity of the white part of the nail, nail thickening, and pain, says Sheth.

Toenail fungal infections can usually be categorized into one of the following five subtypes:

Distal Subungual Onychomycosis This is the most common form of toenail fungal infection, usually occurring in the portion of the nail closer to the tip and on the underside of the nail. The nail may become thick, yellow, or brittle.

Endonyx Onychomycosis People who have endonyx onychomycosis have fungus growing between the layers of the toenails. With this type of fungus, toenails usually have a milky white color and may be pitted or split. They usually don’t thicken or separate from the nail bed.

Proximal White Subungual Onychomycosis This is a relatively uncommon form of toenail fungus, seen most often in people with weakened immune systems due to conditions such as HIV. The fungus enters the toenail through the cuticle and affects the part of the nail closer to the base, turning it a whitish color.

White Superficial Onychomycosis This is also a rare form of toenail fungus that can occur in people who are otherwise healthy. It’s caused by a specific fungus that grows on the superficial, or top, layers of the toenail. Symptoms include opaque, white areas on the toenail that may eventually spread to cover the entire nail. The nail becomes soft and crumbly in texture.

Candida Infection of the Nail Candida is probably best known for causing vaginal yeast infections, but the fungus also lives on the skin. When there’s a break in the skin around the nail, called the nail folds, candida may enter and cause inflammation and infection. The nail itself may thicken and separate from the nail bed if the infection persists. “This type of fungal infection tends to affect fingernails more than toenails,” Goad says.

Conditions That May Look Like Toenail Fungus

Several health conditions can affect the appearance of your toenails and may be mistaken for toenail fungus.

Psoriasis Psoriasis can cause red, scaly patches on the skin. More than half of people with skin psoriasis also have it on their nails. Toenails and fingernails affected by psoriasis may be thick, discolored, crumbly, or loose. “Some people will have nail changes with psoriasis, and if it affects the matrix (the growth plate), then these changes are permanent,” says Sheth.

Skin Cancer A discolored spot underneath a toenail may be a sign of melanoma, a potentially fatal form of skin cancer. Melanoma under a toenail usually looks like a brown or black streak or may appear similar to a bruise. Although this isn’t common, it’s also not rare, says Sheth. Her advice: “It’s always good to check it out.”

Darier Disease This genetic disorder typically causes yellowish, wartlike blemishes on the body. However, some people with Darier disease also have fingernail or toenail irregularities, such as nails that are marked with red and white streaks, according to Genetics Home Reference. Sheth notes, however, that she’s never had a biopsy come back with a diagnosis of Darier disease.

Yellow Nail Syndrome This rare condition has been known to cause slow-growing, thickened, yellow nails, along with abnormalities affecting the lungs and other parts of the respiratory tract and swelling in various parts of the body, according to the National Organization for Rare Disorders. The exact cause of the syndrome is unknown.

Alopecia Areata This autoimmune disorder most commonly causes round patches of hair loss from the scalp, although it can affect other areas of the body as well, according to Genetics Home Reference. Alopecia areata can also affect nails, which may become rough or pitted or develop white spots. Although rare, people with alopecia areata can notice nail changes before they start seeing hair loss.

Diagnosing and Treating Toenail Changes

If you notice changes in the appearance of your toenails, see a doctor promptly. If a fungal infection is suspected, a sample of the nail can be taken and analyzed by a lab to make a diagnosis. If the test comes back positive, an oral or topical antifungal medication may be prescribed to treat the fungus. Most antifungal medications are effective against most forms of toenail fungus, although treatment can take some time, in part because it’s hard to deliver any type of medication through the nail plate to the skin under the nail.

“Most of the time, the treatment requires the whole nail to grow out, which can take up to a year,” says Sheth. “Treatment needs to be consistent and long-term if it has any chance of working.”

If the test comes back negative for fungus, your doctor may begin investigating other causes for the abnormal appearance of your toenails. Sometimes symptoms involving other parts of the body help point to a diagnosis.

People with yellow nail syndrome, for example, may experience leg swelling or breathing problems. Those with alopecia could see their hair begin to fall out.

And, according to Goad, “With psoriasis, patches of red, scaly skin may be seen on the knees, elbows, and face, too. It’s usually not limited to just the toenails.”

Additional reporting by Susan Jara