What Does Toenail Fungus Look Like? Photos by Stage

Toenail fungus typically starts as a small white or yellowish spot near the tip of the nail, then gradually spreads inward, thickening and discoloring the nail as it progresses. By advanced stages the nail can become completely crumbly, dark, and distorted beyond recognition. The infection moves slowly enough that many people miss its earliest signs, so understanding what each stage actually looks like can make the difference between a simple treatment and months of frustration.

What the Earliest Stage Looks Like

The most common form of toenail fungus begins at the free edge of the nail or along one side, then creeps backward toward the cuticle. Doctors call this pattern distal and lateral subungual onychomycosis, and it accounts for the vast majority of cases. In this early phase you might notice a streak or patch of discoloration near the tip of the nail. The colors are usually white, yellow, or light brown, and the affected area often has faint longitudinal streaks running along the nail’s length rather than a uniform blotch.¹ The nail itself still feels mostly firm at this point, and the shape hasn’t changed much. Because the discoloration can be subtle and painless, many people assume the nail is simply stained or bruised.

A second early pattern is worth knowing about. Sometimes toenail fungus appears as chalky white patches on the top surface of the nail rather than creeping underneath it. This is called white superficial onychomycosis, and it looks quite different from the distal-lateral type. Instead of yellow streaks advancing from the tip, you see powdery white spots scattered across the nail plate. The surface may feel rough or slightly gritty when you run a finger over it. This form tends to be easier to treat because the fungus sits on the surface rather than burrowing beneath the nail.

A third and rarer pattern starts at the cuticle end and grows outward toward the tip. This proximal subungual form often shows up as a whitish area near the base of the nail that slowly expands. It’s less common in otherwise healthy people and is sometimes associated with weakened immune function.

What the Middle Stages Look Like

As the infection progresses over weeks to months, the discolored zone expands. What was a small streak at the nail tip now covers a third or more of the nail surface. The color deepens from pale yellow to a more pronounced yellow-brown, and you start to see physical changes beyond color alone. The nail thickens, sometimes unevenly, making it difficult to trim with standard clippers. The edges may become ragged or crumbly, and small pieces of nail may break off on their own.

Underneath the nail, a buildup of debris begins to accumulate. This debris is a mixture of dead skin cells, fungal material, and keratin, and it pushes the nail upward from the nail bed. If you look at the nail from the side, you can often see a gap forming between the nail plate and the skin underneath. This separation, called onycholysis, is one of the clearest visual signs that a fungal infection has moved past its earliest phase. The lifted portion of the nail often appears opaque and whitish compared to the still-attached pink section.

At this stage, you might also notice thickening of the skin directly beneath the nail. This subungual buildup can push the nail up enough that shoes become uncomfortable, and the thickness makes the nail look hump-backed or raised compared to your other nails. Some people describe a faint odor as well, though that is not universal.

Advanced and Total Nail Destruction

Left untreated for months or years, toenail fungus can reach a stage called total dystrophic onychomycosis, where the entire nail is affected. At this point the nail may be thickened several times its normal depth, deeply discolored in shades of brown, yellow, or near-black, and so brittle that large sections crumble away. The normal smooth, translucent appearance of a healthy nail is completely gone. One published case documented a 26-year-old woman whose great toenails on both feet were 100 percent involved after at least five years of untreated infection.²

In severe cases the nail plate itself can partially detach or become so deformed that it curls inward or grows at an angle. The nail bed, now exposed or covered only by a thin, irregular remnant of nail, may look raw and inflamed. Walking can become painful because the thickened, misshapen nail presses against the inside of shoes. At this stage the infection is also much harder to treat, because topical antifungal solutions struggle to penetrate the thick, distorted nail.

What Different Colors Actually Mean

Color is one of the most useful visual clues, but it’s not as straightforward as “yellow equals fungus.” Different hues can suggest different organisms, different severity levels, or even a completely different condition.

White to pale yellow: The most classic early-stage fungal color, usually caused by dermatophyte fungi. White patches sitting on the surface suggest white superficial onychomycosis specifically.
Deep yellow to brown: Indicates the infection has been present longer and has penetrated deeper into the nail. The darker color comes partly from the fungal material and partly from debris accumulating under the nail. A study of distal-lateral onychomycosis found that white, yellow, and brown were the dominant color changes associated with this form.¹
Green or greenish-black: A green discoloration usually signals a bacterial co-infection rather than fungus alone. Certain bacteria thrive in the moist gap between a lifted nail and the nail bed, producing pigments that stain the nail green.
Dark brown to black: This can be fungal, but it can also be a subungual hematoma (blood under the nail from trauma) or, rarely, melanoma. Any dark streak or spot under a toenail that does not grow out with the nail should be evaluated by a doctor.

The color alone is never enough for a definitive diagnosis. Dermatologists rely on it as one piece of the puzzle alongside texture, pattern, and lab results.

How Doctors Score Severity

Toenail fungus is the single most common nail condition, and its severity is most often judged visually.³ To make those visual judgments more consistent, researchers developed the Onychomycosis Severity Index (OSI). The score combines three factors: how much of the nail’s surface area is affected, how close the infection has crept toward the growth center of the nail (the matrix near the cuticle), and whether certain worrisome features are present, such as a thick streak of fungal material within the nail or significant buildup beneath it. Mild cases score between 1 and 5, moderate cases fall between 6 and 15, and severe cases score 16 to 35.⁴

Validation studies have confirmed that different doctors using this index arrive at consistent severity grades, which is useful both for deciding on treatment and for tracking progress over time.⁵ For you at home, the practical takeaway is that two things matter most when assessing how bad your situation is: the percentage of nail surface that’s discolored or damaged, and whether that damage has reached the base of the nail near the cuticle. A small spot at the tip with no thickening is mild. Involvement of more than half the nail, or any sign that the infection has reached the cuticle end, puts you into moderate-to-severe territory where topical treatments alone are less likely to work.

Which Fungus Is Responsible and Whether It Changes the Appearance

Most toenail fungus is caused by dermatophytes, a group of fungi that specialize in breaking down keratin, the protein your nails and skin are made of. In a study of 237 patients with confirmed toenail fungus, about three-quarters were infected with dermatophytes, with Trichophyton mentagrophytes accounting for roughly 47 percent and Trichophyton rubrum for about 28 percent. The remaining quarter were caused by non-dermatophyte molds, including Scytalidium dimidiatum at about 17 percent and Fusarium species at around 7 percent.⁶

This matters visually because the non-dermatophyte infections sometimes look a bit different. Dermatophyte infections tend to produce the classic yellow-brown discoloration and thickening pattern most people associate with toenail fungus. Non-dermatophyte molds can create more varied appearances, including streaky brown or black discoloration that may be confused with melanoma or trauma. In the same study, no patients with non-dermatophyte infections had fungal skin infections beyond the feet, while dermatophyte patients were more likely to have a family history of superficial fungal infections and to show involvement at other skin sites.⁶ So if you have toenail changes but no athlete’s foot or fungal patches anywhere else, a non-dermatophyte cause is worth considering.

Conditions That Look Like Toenail Fungus but Aren’t

One of the biggest pitfalls with toenail fungus is assuming any discolored or thickened toenail must be fungal. Studies consistently show that a significant share of clinically suspected fungal nails test negative when the lab results come back. Several conditions mimic toenail fungus closely enough to fool even experienced clinicians.

Nail psoriasis is the most common lookalike. It can cause thickening, crumbling, discoloration, and separation from the nail bed, all of which overlap with fungal signs. Features that lean toward psoriasis rather than fungus include tiny pits in the nail surface, salmon-colored or oily-looking spots beneath the nail, and splinter hemorrhages (thin reddish-brown lines running lengthwise).⁷ Fungal nails, by contrast, more commonly show the longitudinal streaks and jagged or spiked discoloration patterns visible under magnification. Making things harder, psoriasis and fungus can co-exist in the same nail, so having one doesn’t rule out the other.

Traumatic nail dystrophy is another common mimic. Repeated pressure on the toenails from running, hiking, or tight shoes can cause thickening, discoloration, and lifting that looks identical to fungal infection. A subungual hematoma (bruise under the nail) can produce a dark red, brown, or black spot that grows out over months, sometimes mistaken for a dark fungal infection. And lichen planus, an inflammatory condition, can thin and ridge the nails in ways occasionally confused with early fungal damage.

Because visual appearance alone is unreliable, definitive diagnosis requires lab testing. The standard approaches include dissolving nail clippings in potassium hydroxide solution to look for fungal elements under a microscope, culturing nail samples to identify the specific organism, and in some cases examining nail tissue under histopathology.⁸ If you’re considering oral antifungal medication, which requires months of treatment and carries potential side effects, confirming the diagnosis with a lab test is worth the extra step.

The Connection Between Athlete’s Foot and Toenail Fungus

Many cases of toenail fungus don’t start in the nail at all. They begin as a skin infection on the foot, and the fungus eventually migrates from the skin around the nail folds into the nail itself.⁹ This is why you’ll often see scaling, redness, or peeling skin between the toes or on the soles of the feet alongside early toenail changes. If you treat the nail but ignore the skin infection, reinfection is almost inevitable because the reservoir of fungus is still there.

Visually, look at your feet as a whole rather than fixating on the nail alone. Dry, flaky skin between the fourth and fifth toes, a “moccasin” pattern of scaling across the sole, or small blisters along the arch are all signs of active athlete’s foot. When you see these alongside nail discoloration, the picture points strongly toward fungus rather than trauma or psoriasis. Addressing the skin infection simultaneously, usually with a topical antifungal cream, improves the odds that your nail treatment will actually stick.

Why Toenail Fungus in People With Diabetes Is More Serious

For most healthy adults, toenail fungus is a cosmetic annoyance. For people with diabetes, it carries genuinely elevated medical risks. The infection is both more common and more severe in this group, and it’s linked to complications including secondary bacterial infections, foot ulcers, and in advanced cases, amputation.¹⁰ The reasons stack up: reduced blood flow to the feet slows healing, nerve damage (neuropathy) means injuries and infections go unnoticed, and impaired immune function gives the fungus an easier foothold.

Visually, diabetic patients often present with more extensive nail involvement at the time of diagnosis, simply because reduced sensation means they’re less aware of early changes. Thickened, jagged fungal nails can also cause small cuts in the surrounding skin, and in a foot with compromised circulation, those tiny wounds can become entry points for bacteria. A secondary bacterial infection layered on top of a fungal nail can escalate quickly. If you have diabetes and notice any of the nail changes described earlier, even a small discolored spot at the tip, it’s worth getting it checked rather than waiting to see how it develops.¹¹

Toenail Fungus in Children

Toenail fungus is overwhelmingly an adult problem, but it does occasionally occur in children. A systematic review examining multiple studies found that the prevalence of toenail fungus in children ranged from about 0.1 percent to roughly 3 percent, compared to much higher rates in adults.¹² Toenails were more commonly affected than fingernails in most studies, mirroring the pattern seen in adults.

In children, the visual presentation tends to be milder: a small white or yellowish patch, usually at the tip of the big toenail, without the dramatic thickening and crumbling seen in longstanding adult cases. Children’s nails grow faster than adult nails, which actually works in their favor because the nail turns over more quickly and the fungus has less time to establish itself. When a child does develop visible toenail changes, it’s important to consider the mimics mentioned earlier, especially trauma from sports or tight shoes, which is extremely common in active children and can look nearly identical to early fungal infection. Lab confirmation is particularly worthwhile in pediatric cases before committing to treatment.

What Healing Looks Like

Once treatment starts working, the visual recovery is slow and follows a distinctive pattern that catches many people off guard. You will not see the existing discolored nail return to normal. Instead, a new, healthy-looking nail grows from the base, gradually pushing the damaged portion forward. This means you’ll have a two-toned nail for months: clear and pink near the cuticle, discolored and thick toward the tip. The boundary between old damage and new growth should move steadily toward the end of the toe over time.

Toenails grow roughly one to two millimeters per month, so replacing an entire big toenail takes somewhere around 12 to 18 months. During this time the temptation is to assume treatment has failed because the nail still looks bad at the tip. What you’re actually looking for is whether that clear zone at the base is expanding. If it is, treatment is working even though the visible result is still months away from completion. If the new nail emerging from the cuticle also appears discolored or thickened, that’s a genuine sign the infection hasn’t been controlled and it’s time to reassess with your doctor.

Some practical visual markers of progress include a smooth, uniform texture on the new-growth portion, a return of the pinkish color that comes from seeing the nail bed through a clear nail, and a clean line of demarcation between old and new nail. The damaged section ahead of that line may continue to crumble and break off, which is actually a good thing because it shortens the time until the entire nail looks healthy again. Trimming the affected portion as it reaches the free edge helps speed up the cosmetic improvement.