Nail fungus starts when microscopic fungi slip through tiny gaps in or around your nail, then feed on the hard protein (keratin) that makes up the nail plate. Preventing it comes down to three things: keeping your feet dry, avoiding contact with the fungus in the first place, and eliminating the micro-damage that gives it a way in. About 90% of toenail infections are caused by a group of fungi called dermatophytes, which thrive in warm, moist environments like showers, pool decks, and sweaty shoes.
How the Fungus Gets In
Nail fungus doesn’t appear out of nowhere. The fungi produce enzymes that break down keratin, allowing them to burrow into your nail. The most common entry point is the far edge of the toenail, where the nail meets the skin underneath. From there, the fungus migrates slowly toward the base of the nail. Less commonly, it can enter through the cuticle area or land directly on the nail’s surface, creating white, chalky patches.
This means anything that creates a gap between your nail and the surrounding skin is essentially rolling out the welcome mat. Stubbing your toe, wearing shoes that press against the nail, or trimming too aggressively can all create micro-openings. Athlete’s foot is another major gateway: the same fungus that causes itchy, peeling skin between your toes can spread to the nail if left untreated.
Keep Your Feet Dry
Moisture is the single biggest factor you can control. Dermatophytes need a damp environment to grow, and your feet produce more sweat per square inch than almost any other part of your body. Every hour your feet sit in damp socks or shoes is an hour the fungus has ideal growing conditions.
Change your socks whenever they feel damp, even if that means swapping them midday. The fabric matters more than most people realize. Cotton absorbs moisture well but stays wet against your skin, creating exactly the clammy environment fungi love. Merino wool is a better choice: it can absorb up to three times its weight in moisture while still feeling dry on the surface, thanks to a water-repelling outer layer and an absorbent inner core. It also dries faster than polyester. Your best option is a thin, lightweight sock that blends merino wool with synthetic fibers like nylon or Coolmax, which wick sweat away from the skin while the wool absorbs it.
After showering, bathing, or swimming, dry your feet thoroughly, including between each toe. A quick towel-off isn’t enough. Those web spaces between toes stay damp longest and are where athlete’s foot typically starts before spreading to the nails.
Rotate and Treat Your Shoes
Shoes can harbor fungal spores for weeks. If you wear the same pair every day, it never fully dries out, and you’re reintroducing your feet to fungus each morning. Rotating between at least two pairs gives each one a full day to air out.
For shoes you suspect are contaminated, especially during or after treating an infection, antifungal sprays applied to the insoles can reduce the fungal load. UV-C shoe sanitizers, which expose the interior to ultraviolet light for 5 to 15 minutes, have shown complete fungal inhibition in laboratory studies. Choose shoes made from breathable materials when possible, and avoid wearing the same athletic shoes for long training sessions without letting them dry between uses.
Protect Your Feet in Shared Spaces
Gym showers, locker room floors, public pools, and hotel bathrooms are all places where dermatophytes live on warm, wet surfaces. Wear shower shoes or flip-flops in any communal wet area. This is probably the single most effective habit for people who use gyms or public pools regularly.
At nail salons, fungal transmission can happen through improperly sterilized tools. If you get pedicures, confirm that metal instruments are autoclaved (sterilized with pressurized steam) between clients, or bring your own set. Avoid shaving your legs right before a pedicure, since small nicks give fungi another potential entry point.
Trim Your Nails the Right Way
Improper nail trimming is a surprisingly common cause of the micro-damage that lets fungi in. Cut your toenails straight across rather than rounding the corners. Rounding or cutting too short can cause the nail edge to dig into the surrounding skin, creating both ingrown nails and tiny wounds that fungi exploit. Use clean, sharp clippers. Dull blades crush and splinter the nail rather than cutting cleanly, leaving rough edges that can snag and separate from the nail bed.
Keep nails relatively short so they’re less likely to catch on socks or shoes and sustain trauma. But don’t cut them so short that you expose the skin underneath. A millimeter or two of free edge is ideal.
Who’s at Higher Risk
Some people need to be more aggressive about prevention because their biology works against them. Diabetes is a major risk factor. High blood sugar damages small blood vessels and reduces sensation in the feet, meaning you may not notice early signs of nail trauma or skin breakdown. Impaired circulation also weakens your local immune response, making it harder for your body to fight off fungal invaders before they establish themselves. If you have diabetes, daily foot inspections and careful nail care aren’t optional extras.
Other factors that raise your risk include older age (nails grow more slowly and thicken with time, giving fungi more to feed on), obesity, peripheral vascular disease, and any condition that suppresses your immune system. People who sweat heavily, wear steel-toed boots or tight shoes for work, or have a history of athlete’s foot are also more vulnerable.
Preventing Recurrence After Treatment
If you’ve already had nail fungus and successfully treated it, prevention becomes even more important. Recurrence rates range from about 10% to over 50% depending on the study, with reinfection sometimes appearing a year or more after the nail looks clear. Two factors most strongly predict recurrence: having diabetes and having had severe nail involvement (more than half the nail affected) at the time of the original infection.
Some dermatologists recommend applying a topical antifungal to the nails and surrounding skin after completing treatment to delay reinfection. The evidence for this is mixed. In one follow-up study, applying antifungal lacquer once weekly didn’t clearly prevent relapse, though twice-weekly application appeared to delay recurrence by roughly 200 days. If your doctor recommends post-treatment prophylaxis, the suggested duration is at least two to three years, and for people with diabetes or severe prior infections, it may need to continue indefinitely.
Treating any lingering athlete’s foot is critical during this window. The fungus living on the skin of your feet is the most common source of reinfection. Applying antifungal cream to the soles and between the toes, even when the skin looks normal, can help keep the fungal population low enough to prevent it from re-colonizing the nail. Combine this with the footwear, sock, and hygiene habits above, and you give yourself the strongest defense against going through the whole treatment process again.