Toenail fungus affects roughly 10% of the general population worldwide, making it one of the most common nail conditions. That number climbs sharply with age, reaching 20% in people over 60 and 30% in those over 70. It’s far from rare, and if you’re dealing with it, you’re in very large company.
Who Gets It Most Often
Age is the single biggest factor. In children, toenail fungus is genuinely uncommon, affecting only about 0.3% of the pediatric population. The infection becomes progressively more likely with each decade of life, largely because nails grow more slowly as you age (giving fungi more time to take hold), blood circulation to the feet decreases, and cumulative exposure to the fungus adds up over the years.
Men are significantly more likely to develop toenail fungus than women. A large case-control study of over 1,200 patients with nail problems found that women had roughly 40% lower odds of having a fungal infection compared to men, even though women actually showed up more often with nail changes overall. The reasons aren’t entirely clear, but differences in footwear habits, occupational exposure, and hormonal factors all likely play a role.
Athletes face about 2.5 times the risk of the general population. The combination of intense training, restrictive shoes that trap heat and moisture, and shared locker rooms and showers creates ideal conditions for the fungi that cause these infections. Swimmers, runners, and anyone who spends long hours in athletic footwear are particularly vulnerable.
What Actually Causes the Infection
Over 90% of toenail fungal infections are caused by just two species of dermatophytes, a family of fungi that feed on the protein keratin in your nails, skin, and hair. The most common culprit is responsible for about 60 to 65% of cases, with a closely related species accounting for another 30 to 35%. The remaining infections come from yeasts and environmental molds, which together cause roughly 7% of fungal nail infections.
These organisms thrive in warm, moist environments. Sweaty feet inside closed shoes, damp bathroom floors, and pool decks are classic transmission points. People with poor circulation, diabetes, or a weakened immune system face higher risk because their bodies are less effective at fighting off the fungus before it establishes itself in the nail.
Not Everything That Looks Like Fungus Is Fungus
One important detail that many people don’t realize: a thick, discolored, or crumbly toenail isn’t automatically a fungal infection. Orthopedic problems are actually considered as common as, or possibly even more common than, fungus as a cause of toenail changes. Mechanical irritation from tight shoes, overlapping toes, or an uneven gait can produce nail damage that looks nearly identical to a fungal infection. There’s even a recognized condition caused by asymmetric walking patterns that is routinely mistaken for toenail fungus.
Nail psoriasis is another frequent lookalike. The two conditions share so many visual and even microscopic features that specialists with decades of experience consider them the most important conditions to distinguish from each other. This is why getting a proper diagnosis, typically through a nail clipping or scraping sent to a lab, matters before starting treatment. Antifungal medications won’t help a nail problem that isn’t actually caused by a fungus.
How Likely It Is to Come Back
Even after successful treatment, toenail fungus has a relapse rate of 20% to 25%, with most recurrences happening within two years. This high return rate is partly because the same risk factors that caused the original infection, like foot anatomy, shoe choices, and exposure to communal wet surfaces, are still present after treatment ends. Older adults tend to have both lower response rates and higher relapse rates than younger patients.
The slow growth of toenails compounds the problem. A big toenail takes 12 to 18 months to fully grow out, meaning you won’t know if treatment truly worked for quite some time. During that long window, reinfection is possible if the fungus is still present in your environment, your shoes, or on the surrounding skin of your feet. Athlete’s foot, a fungal skin infection on the foot caused by the same organisms, is one of the strongest predictors of developing toenail fungus in the first place, so keeping the skin around your nails healthy is just as important as treating the nail itself.
Practical Ways to Lower Your Risk
Since warm, moist conditions are the common thread across nearly every risk factor, keeping your feet dry is the most effective prevention strategy. That means changing socks when they get damp, choosing moisture-wicking materials, alternating between pairs of shoes so each pair has time to dry out fully, and wearing sandals or shower shoes in locker rooms and public pools.
Trimming nails straight across and keeping them short reduces the surface area available for fungi to colonize. If you’ve had a previous infection, treating your shoes with antifungal sprays or UV shoe sanitizers can help reduce the fungal load in your footwear. And because athlete’s foot on the surrounding skin is such a strong gateway to nail infection, treating any itchy, peeling, or cracked skin between your toes promptly can prevent the fungus from migrating into the nail.