Toenail fungus typically starts as a white or yellow-brown spot under the tip of the nail. As the infection spreads deeper, the nail thickens, changes color, and begins to crumble at the edges. It’s the most common nail disorder in adults, affecting up to 5% of people at any given time and as many as 20% over a lifetime. Fungus can also appear on the skin between your toes, where it causes scaly, peeling, or cracked patches.
Early Signs: What the First Spot Looks Like
In the first four to six weeks, toenail fungus is easy to miss. You might notice a small discolored spot near the tip of the nail, usually white, yellowish, or light brown. The nail may start to lift slightly from the nail bed underneath, and there can be mild thickening that you feel more than you see. At this stage, the nail still looks mostly normal, which is why many people don’t realize anything is wrong.
The infection almost always begins at the free edge of the nail (the part you trim) and works its way back toward the cuticle. This is the most common pattern, and it’s worth paying attention to because early-stage fungus is significantly easier to treat than advanced infections.
Moderate Stage: Discoloration and Crumbling
By two to three months, the changes become harder to ignore. The discoloration intensifies, turning deeper yellow, brown, or even brownish-black. The nail gets noticeably thicker and may start to feel uncomfortable in shoes. Edges become brittle, crumbly, or ragged, and small pieces of the nail may chip off on their own.
You might also notice a chalky, powdery debris building up underneath the nail. This is a buildup of skin cells that the fungus disrupts as it grows between the nail and the nail bed. The debris pushes the nail upward, making it look raised or warped compared to your healthy nails.
Advanced and Chronic Infections
After six months or more without treatment, toenail fungus can cause severe structural damage. The nail thickens dramatically, becomes deeply discolored, and may develop a misshapen or twisted appearance. In some cases, the nail separates almost completely from the nail bed, a condition where the nail looks like it’s floating or barely attached. The nail can also develop a noticeable smell.
Chronic infections that persist beyond a year can destroy the nail entirely. The nail plate loses its normal structure, and the nail may fall off or become so damaged that regrowth is unlikely without treatment. At this stage, the infection frequently spreads to neighboring toenails. Walking can become painful, especially in closed shoes, because the thickened nail presses into the surrounding skin.
Less Common Patterns to Recognize
Not all toenail fungus follows the classic tip-to-cuticle pattern. Some types create distinct visual signatures worth knowing about:
- White powdery patches on the surface. Instead of starting under the nail, this type grows on top. It looks like chalky white streaks or spots across the nail surface, almost as if someone dusted flour on it.
- White discoloration starting near the cuticle. This rarer pattern begins at the base of the nail and spreads outward toward the tip. You’ll see a white area forming near the cuticle with debris accumulating underneath.
- Milky white nail with splitting layers. The entire nail takes on a cloudy, milky appearance and may split into thin horizontal layers, but without the thick debris buildup or nail lifting seen in other types.
Fungus on the Skin Between Your Toes
Fungal infections don’t only affect nails. Athlete’s foot targets the skin itself, especially the warm, moist spaces between your toes. It looks like scaly, peeling, or cracked skin in those gaps. The affected skin may appear red on lighter skin tones, or purple to grayish on darker skin tones. It can also cause swelling, itching, and a burning sensation.
Athlete’s foot and toenail fungus are caused by the same types of organisms, and one can lead to the other. If you notice peeling skin between your toes alongside nail changes, both areas likely need attention.
How to Tell It Apart From Nail Psoriasis
Nail psoriasis can look similar to fungus at first glance, with thickening, discoloration, and nail lifting. But there are reliable visual differences.
Psoriasis causes tiny pits or dents in the nail surface that look like someone pressed a thumbtack into the nail. These small, shallow depressions don’t occur with fungal infections. Psoriasis also produces reddish or dark brown splotches on the nail called “oil spots,” which fungal infections don’t cause. Another clue: if just one toenail is affected, it’s much more likely to be fungus or trauma than psoriasis. Psoriasis tends to involve multiple nails and usually shows up alongside skin plaques elsewhere on the body.
One more distinguishing detail: when the nail lifts from the bed in psoriasis, there’s often a reddish line at the border between the attached and detached portions, almost like a lipstick line. Fungal nail lifting doesn’t produce this colored border.
What Nail Color Can Tell You
The color of the nail offers clues about what’s going on underneath. A yellowish or yellow-white nail is the most common presentation and points to a standard fungal infection that’s been progressing for a few weeks to months. Brown or brownish-black nails suggest a deeper, longer-standing infection where debris has been accumulating for some time. A bright white or milky nail, especially without significant thickening, may indicate a less common fungal subtype.
Keep in mind that trauma (stubbing a toe, dropping something on it) can also cause dark discoloration from blood pooling under the nail. Traumatic discoloration tends to grow out with the nail over several months and doesn’t cause the progressive thickening and crumbling that fungus does.
How Long Treatment Takes
Toenail fungus responds slowly to treatment because the nail itself grows slowly. A standard course of oral antifungal medication lasts about three months, but it can take six months to a full year for the nail to look completely normal again. You’re essentially waiting for a healthy nail to grow in and replace the damaged one.
Topical treatments applied directly to the nail work best for mild, early-stage infections. More advanced cases typically need oral medication because topical agents can’t penetrate a thickened nail well enough to reach the fungus underneath. The earlier you catch the infection, the shorter and simpler the treatment tends to be.
People With Diabetes: Extra Caution
If you have diabetes, toenail fungus and athlete’s foot carry additional risks. Reduced blood flow and nerve damage in the feet mean that small infections can escalate quickly. The CDC flags thick, yellow toenails, dry cracked skin on your feet, and fungal infections between your toes as signs that warrant a visit to your doctor. Even seemingly minor foot problems in people with diabetes can lead to serious complications if left untreated, so prompt attention to any nail or skin changes on your feet is important.