Toenail fungus typically shows up as a white, yellow, or brown discoloration that starts at the edge or tip of the nail and gradually spreads. As the infection progresses, the nail thickens, becomes cloudy or chalky in spots, and may crumble or break apart at the edges. About 4% of the general population has a toenail fungal infection at any given time, and it can look quite different depending on the type and stage.
The Earliest Signs
In its earliest stage, toenail fungus is easy to miss. You might notice a small white or yellowish spot near the tip or side of the nail. The nail may look slightly cloudy in one area, almost like a smudge that doesn’t wipe away. At this point there’s usually no pain, no thickening, and no crumbling, which is why many people ignore it for months.
That initial spot is the fungus working its way under the nail plate. It feeds on keratin, the protein that makes up your nail, and slowly breaks down the nail’s structure from within. Without treatment, that small discolored patch will spread toward the base of the nail over weeks to months.
The Most Common Pattern
The type of toenail fungus most people get starts at the free edge of the nail (the part you trim) or along one side, then works inward. The infected area turns yellow-white and the nail begins to separate from the nail bed underneath. You’ll often see yellow streaks running through the central part of the nail plate. Chalky, crumbly debris starts to build up under the nail, which pushes the nail upward and makes it look thicker than normal.
This buildup of debris is one of the hallmarks of a fungal infection. If you trim the nail short, you may see a soft, powdery, yellowish material packed underneath. The nail itself becomes harder to cut because of the thickening, and the edges may look ragged or uneven.
Chalky White Patches on the Surface
A less common pattern produces white, chalky spots directly on the surface of the nail rather than underneath it. These patches sit on top and can actually be scraped off with a nail file or similar tool. The nail surface feels rough and powdery in the affected areas. This type tends to stay superficial for longer before causing the deep thickening and crumbling seen with other forms.
Discoloration Near the Cuticle
In rarer cases, the infection enters from the base of the nail near the cuticle and moves outward toward the tip. This pattern produces a white or yellowish area on the half-moon (lunula) at the base of the nail. Over time it can cause the nail to lift away from the bed near the cuticle, with visible thickening and destruction of the nail plate closest to the skin fold. This type is uncommon in otherwise healthy people and is sometimes associated with a weakened immune system.
What Severe Infections Look Like
Left untreated for months or years, toenail fungus can destroy the entire nail. The nail becomes opaque and yellow-brown throughout, significantly thicker than a healthy nail, and crumbly or ragged across its whole surface. It may warp into an irregular shape, curving or bulging in ways that make wearing shoes uncomfortable. In some cases, debris buildup becomes so extensive that the nail lifts almost entirely off the nail bed.
At this stage, the surrounding skin may also be affected. Yeast infections (a different type of fungus) can cause the skin around the nail to become red, swollen, and tender to the touch. The nail fold along the sides or base of the nail may look puffy and inflamed. In severe cases, the nail can detach completely from the nail bed.
Some people also notice a stale, slightly foul smell coming from the affected nail, particularly when trimming it. This odor comes from the fungal organisms and the decomposing keratin debris trapped beneath the nail plate.
Fungus vs. a Bruise Under the Nail
A dark spot under the toenail can be either a bruise (from dropping something on your toe or repetitive pressure from shoes) or a fungal infection. There are three reliable ways to tell them apart.
- Shininess: A bruise under the nail looks shiny and has a uniform color with clean edges. Fungal discoloration looks dull, foggy, or opaque because the fungus breaks apart the nail’s keratin layers and changes how light passes through.
- Movement: A bruise gets carried forward as the nail grows out. Take a photo, note the distance from the cuticle to the dark spot, then check again two weeks later. If that distance has increased, it’s a bruise moving with the nail. Fungal infections stay in place or spread backward toward the cuticle.
- Spreading: If the dark area is getting larger over time rather than simply shifting position, that points to fungus, not a bruise.
Fungus vs. Nail Psoriasis
Nail psoriasis can look strikingly similar to a fungal infection, with thickening, discoloration, and nail separation from the bed. A few visual clues can help distinguish them. Psoriasis often causes tiny dents or pits across the nail surface, like someone poked the nail with a pin. It can also produce distinctive salmon-colored or oily-looking yellowish spots on the nail bed (sometimes called “oil drop” spots). Fungal infections rarely cause pitting. If you have psoriasis patches on your skin elsewhere, especially on your elbows, knees, or scalp, nail psoriasis becomes more likely. That said, it’s possible to have both conditions at the same time, and a nail clipping sent to a lab is the only way to confirm fungus for certain.
Which Toenails Are Most Affected
The big toenail is by far the most common site. It’s the largest nail, takes the most impact inside shoes, and has the slowest growth rate, giving fungus more time to establish itself. The pinky toenail is the second most common, likely because it also takes significant pressure from footwear. Any toenail can be affected, and infections can spread from one nail to the next over time, so catching it early on a single nail is easier to manage than waiting until several are involved.