How Common Is Toenail Fungus and Who Gets It?

Toenail fungus affects roughly one in ten people in the general population, making it one of the most common nail disorders worldwide. The numbers climb steeply with age: about one in five people over 60 and as many as half of those over 70 have it.¹ But those headline figures mask wide variation depending on sex, underlying health conditions, lifestyle, and even genetics, which means your personal odds could be much higher or much lower than average.

How Common It Really Is Depends on How You Count

Prevalence estimates for toenail fungus range widely across studies, partly because researchers define and detect it differently. When researchers screened people regardless of whether they had visible nail symptoms, the pooled rate of toenail infections caused by the main fungal group was about 4 percent.² That number is deliberately conservative because it counts only lab-confirmed cases of one fungal type. Broader clinical estimates that include all causative fungi and rely on a mix of clinical and laboratory diagnosis put the figure closer to 10 percent of the overall population.¹ Both figures are credible; they just answer slightly different questions. What nobody disputes is that toenail infections vastly outnumber fingernail infections, and that the condition is found more often in toenails across every population studied.³

Age Is the Single Biggest Risk Factor

If there is one reliable predictor of toenail fungus, it is getting older. Prevalence roughly doubles with each decade after age 50, and some estimates put the rate in people over 70 at about half.¹ Several things converge in older adults to make this happen: nails grow more slowly, giving fungi longer to colonize; blood flow to the feet diminishes; immune surveillance weakens; and accumulated years of minor nail trauma add up. Older adults were found to carry nearly five times the risk of the general population in a large pooled analysis of special populations.²

Children, by contrast, are rarely affected. Prevalence in kids is estimated at under 1 percent.⁴ Their nails grow faster, their feet tend to stay drier, and they have less cumulative exposure to the environments where fungi thrive.

Men Get It More Than Women

Both population-wide studies and hospital data show that toenail fungus is more common in men than in women.³ The exact reasons are debated, but men tend to wear closed-toe shoes for longer stretches, sustain more repetitive foot trauma through physical labor and sports, and are historically less likely to seek early treatment for a cosmetic complaint. Hormonal differences may also play a role, though the evidence there is thinner. One interesting wrinkle from diagnostic studies: when men did present with nail problems, clinical accuracy in diagnosing fungus was higher for them, suggesting that by the time men show up, the infection has often progressed further and is easier to spot.⁵

Medical Conditions That Multiply the Risk

Certain health conditions dramatically raise the likelihood of toenail fungus. A 2024 meta-analysis quantified the relative risk for several groups compared with the general population:²

• Knee osteoarthritis: nearly 15 times the general-population risk, the highest of any group studied. Reduced mobility likely plays a part, along with chronic inflammation and possibly the medications used to manage joint disease.
• Chronic venous disease: about 6 times the risk. Poor circulation in the legs creates an environment that favors fungal growth.
• Organ transplant recipients: roughly 5 times the risk, driven by the immune-suppressing drugs needed to prevent rejection.
• HIV: about 4 times the risk. An impaired immune system makes it harder to clear fungal invaders from the nail bed.
• Diabetes: roughly 3 times the risk, with up to a third of people with diabetes affected. Nerve damage and reduced blood flow to the feet combine to create a perfect habitat for fungi.
• Lupus and hemodialysis patients: each about 3 times the risk.

What ties most of these conditions together is some combination of weakened immunity, impaired blood flow, and altered nail structure. In people with diabetes specifically, the presence of nerve damage paired with poor circulation in the foot was the strongest predictor of toenail fungus.⁶ For immunocompromised people more broadly, the species of fungus involved can differ from what typically infects healthy adults, and the infection can be harder to diagnose because the clinical presentation may look unusual.⁷

Why Athletes and Active People Are Vulnerable

Athletes are about two and a half times more likely to develop toenail fungus than the general population.⁴ The reasons are straightforward: tight, occlusive shoes trap moisture around the toes; sweat keeps the skin damp for hours; shared locker rooms and showers expose feet to fungal spores; and repetitive impact to the toes causes micro-damage to nails. Runners, swimmers, and soccer players show up frequently in the literature. The trauma angle is worth highlighting on its own, because even a single significant injury to a toenail, whether from sports or from dropping something on your foot, can make that nail susceptible to fungal colonization years later.⁸ Researchers suspect that trauma disrupts local blood supply and nerve function in the nail bed, weakening the immune response right where the fungus tries to gain a foothold.

Swimming pools are the exposure most people think of first. In one survey of beauty salon clients, the vast majority of respondents identified swimming pools as the main risk factor for fungal foot infections.⁹ That perception is not wrong, but it is incomplete. Any warm, moist, communal surface where people walk barefoot presents the same type of risk: hotel showers, gym floors, communal saunas. The fungal spores that cause toenail infections can survive for weeks on damp surfaces.

Genetics Can Stack the Deck

Some families seem to pass toenail fungus around like a shared cold, but what is actually being shared may be more than just a contaminated bathroom mat. Research has identified an autosomal dominant pattern of susceptibility linked to the most common toenail fungus species, meaning that if one of your parents had chronic toenail fungus, your own risk is elevated by inheritance, not just by exposure.¹⁰ One mechanism that has been identified involves a mutation in a gene called Dectin-1, which produces a receptor that helps immune cells recognize and bind to fungal organisms. People carrying this variant have reduced ability to mount the immune responses needed to fight off Candida and other fungi. In a separate finding, patients with toenail fungus showed roughly double the level of certain regulatory immune cells compared to healthy controls, suggesting that the immune system in susceptible individuals may be suppressing its own antifungal response.¹⁰

This genetic dimension helps explain a pattern that frustrates many patients: they clear the infection with treatment only to get reinfected when others in the same household never catch it at all. It is not bad luck or poor hygiene. Some people’s immune systems are simply less equipped to keep these particular fungi at bay.

What Fungi Are Actually Responsible

Three broad groups of fungi cause toenail infections: dermatophytes (the most common by far), yeasts, and non-dermatophyte molds. Toenail infections account for up to 30 percent of all diagnosed superficial fungal infections.¹¹ The dominant culprit worldwide is a dermatophyte called Trichophyton rubrum, which genetic studies suggest originated in Africa and later spread to Asia, Europe, and the Americas as human populations migrated and mixed.¹² T. rubrum is remarkably well adapted to human keratin, the protein that makes up nails. It grows slowly enough to avoid triggering a massive immune response, embeds itself within the nail plate, and can persist for years if untreated.

Non-dermatophyte molds and mixed infections are increasingly recognized as a clinical problem, partly because they are harder to identify in the lab and partly because they respond poorly to the standard antifungal drugs designed to target dermatophytes.¹³ When treatment fails, it is worth asking whether the original fungus was correctly identified.

Not Everything That Looks Like Fungus Is Fungus

One of the more practical problems with toenail fungus is that many nail conditions mimic its appearance. Thickened, discolored, or crumbly nails can result from psoriasis, chronic trauma, poor circulation, lichen planus, or simply aging. In one study of Dutch general-practice patients, doctors correctly identified fungal infection based on appearance alone only about three-quarters of the time.⁵ That means roughly one in four patients who look like they have fungus actually have something else, and treating the wrong condition wastes time, money, and potentially liver function (oral antifungals can be hard on the liver).

Lab confirmation matters, and the available tests vary in accuracy. Nail biopsy stained with a special chemical marker has been shown to be the most sensitive single test, catching about 85 to 92 percent of true infections depending on the study.^{14 15} Standard fungal culture, by contrast, has much lower sensitivity, missing 40 to nearly 70 percent of actual infections. Culture is useful because it identifies the specific species of fungus, which matters for choosing the right drug, but a negative culture does not mean you are fungus-free. The practical upshot: if your doctor suspects toenail fungus but the culture comes back negative, it may be worth requesting a biopsy or at least a repeat test before starting treatment or giving up on the diagnosis.

The Psoriasis Overlap

Psoriasis of the nails deserves its own mention because it creates a confusing clinical picture. Psoriatic nails can look nearly identical to fungus-infected nails: pitting, thickening, discoloration, and separation of the nail from the bed are common to both conditions. To make matters more complicated, people with nail psoriasis may actually be more prone to developing genuine fungal infections on top of their psoriasis. The psoriatic nail plate is disrupted and the blood supply to the nail bed is abnormal, which lowers the nail’s natural defenses against fungi. The separation of nail from nail bed that psoriasis causes also creates a humid pocket that fungal organisms love.¹⁶ For someone with psoriasis who suspects they also have fungus, lab testing is especially important because treating fungus alone will not fix a psoriatic nail, and treating psoriasis alone will not clear an actual fungal coinfection.

How It Looks When It Progresses

Toenail fungus is not a single uniform disease. Dermatologists recognize several distinct subtypes based on how and where the fungus enters the nail. The most common form starts at the tip and sides of the nail and works inward. A less common type starts at the base of the nail, near the cuticle, and is sometimes associated with immune problems. There is also a superficial form that creates white powdery patches on the nail surface, and a deep form that invades the nail plate itself without obviously lifting or separating it.¹⁷ In advanced cases, the nail becomes totally destroyed. These subtypes are not just academic categories; they can influence which treatment approach works best and how the infection responds to topical versus oral medication.

It Bothers People More Than Doctors Expect

Because toenail fungus is not life-threatening, it has historically been dismissed as a cosmetic nuisance. But the evidence on quality of life tells a different story. In one study, more than half of patients with toenail fungus said they felt embarrassed by the appearance of their nails, 40 percent actively hid their feet, and about 28 percent said they had developed a complex about the condition.¹⁸ Functional complaints were common too: over half reported spending excessive time on nail care, and 40 percent said wearing shoes was uncomfortable. A systematic review confirmed that the condition affects physical functioning, social interactions, and emotional well-being, and that successful treatment measurably improves mental health scores and daily functioning.¹⁹

For people with diabetes, the stakes go beyond discomfort. Fungal infections of the foot can create breaks in the skin, and there is evidence suggesting that fungal foot infections are a risk factor for bacterial cellulitis in the lower leg, a potentially serious infection that can spread rapidly in people with impaired circulation.²⁰ In immunocompromised patients more broadly, untreated toenail fungus can lead to secondary bacterial infections, ulceration, and in rare cases, systemic fungal spread.²¹

Why It Keeps Coming Back

Even after apparently successful treatment, toenail fungus recurs frustratingly often. The reasons are layered. Toenails grow slowly, so a full treatment course for oral antifungals can last three months and the nail itself may take a year or more to grow out completely. During that long window, reinfection from contaminated shoes, socks, or household surfaces is common. Residual fungal spores in the nail bed that survived treatment can also reactivate once medication stops.

A growing concern is antifungal resistance. The most widely prescribed oral treatment, terbinafine, is increasingly encountering resistant strains, particularly of T. rubrum and a newer species called T. indotineae that has been documented globally. These resistant infections are associated with high rates of relapse and chronic disease.²² Non-dermatophyte molds and mixed infections add another layer of difficulty because they often do not respond to standard first-line drugs at all, and they can be missed or misidentified during diagnosis.¹³ For the subset of patients whose genetic makeup predisposes them to fungal infection, the structural disadvantage persists regardless of how many treatment courses they complete. Accurate species identification before treatment, attention to environmental decontamination afterward, and realistic expectations about recurrence rates together form the practical foundation for managing a condition that, for many people, turns out to be lifelong.