If you run regularly, you’ve probably noticed changes to your toenails over time. Thickening, discolouration, brittleness — these are the hallmarks of onychomycosis (fungal nail infection), and runners get it far more often than the general population. In Sydney, where we train year-round and summer heat pushes sweat levels higher, the risk is compounded. This post explains exactly why runners are at higher risk of toenail fungus, how to tell it apart from other nail conditions, and what you can do to prevent and treat it — without stopping training.
Why Runners Get Toenail Fungus More Often
Onychomycosis is caused by dermatophytes (a group of fungi that feed on keratin, the protein that makes up your nails and skin). These organisms thrive in warm, moist, dark environments — which is a precise description of the inside of a running shoe during a long run.
Several factors specific to running combine to make fungal nail infections far more common in athletes than in the broader community.
Microtrauma: The Entry Point
With every stride, your toes press forward into the toe box of your shoe. Over thousands of repetitions, this creates microtrauma — tiny separations between the nail plate and the nail bed beneath. These microscopic gaps become entry points for fungal organisms. The problem is worse in shoes that are too small, too narrow in the toe box, or that slip at the heel, causing the foot to slide forward. This is why choosing the right running shoes matters well beyond comfort and performance.
Prolonged Moisture from Sweat
A typical one-hour run produces significant moisture inside your shoe. Synthetic shoe materials and cotton socks trap that moisture rather than wicking it away. Dermatophytes need only a small amount of warmth and humidity to establish an infection. When you finish a run and leave your shoes to dry overnight in a dark bag, you’re creating near-perfect fungal growing conditions.
Communal Surfaces and Locker Rooms
Changing rooms at running clubs, race events, gym showers, and public pools are high-risk environments. Walking barefoot on wet surfaces shared by many athletes exposes you to fungal spores directly. This is a well-recognised risk factor in sports podiatry.
Speed Dressing After Training
Many runners pull on socks and shoes immediately after a shower, before feet are fully dry. Moisture between the toes and under the nails at this point is enough to support fungal growth, particularly if tinea pedis (athlete’s foot) is already present.
Athlete’s Foot vs Fungal Nail: Two Different Problems
It’s important to distinguish between tinea pedis (athlete’s foot) and onychomycosis. Athlete’s foot affects the skin — typically causing peeling, itching, and redness between the toes or on the sole. Onychomycosis affects the nail itself.
The clinical distinction matters because the two conditions respond to different treatments. Topical antifungals work well on skin infections but have limited penetration into the nail plate. Nail infections generally require longer treatment courses, and in more established cases, laser treatment.
The link between the two conditions is important for runners to understand: untreated tinea pedis frequently progresses to onychomycosis. The fungus migrates from the skin to the nail bed, often through the same microtrauma entry points caused by repetitive toe-box contact. If you’re treating athlete’s foot but ignoring early nail changes, the infection is likely spreading. Our guide to athlete’s foot covers the distinction in more detail.
What Fungal Nail Looks Like in Runners
In runners, fungal nail infection most commonly affects the hallux (big toe) and the second toenail — the nails that bear the most repetitive pressure. Early signs include:
- White or yellow-brown discolouration beginning at the tip of the nail
- Gradual thickening of the nail plate
- Debris accumulating under the nail (subungual hyperkeratosis)
- Nail becoming brittle or crumbly at the edges
- In advanced cases, the nail lifting from the nail bed (onycholysis)
Black toenails — a common complaint among runners — are usually not fungal. They result from subungual haematoma (bleeding under the nail) caused by the same repetitive microtrauma. A black toenail that doesn’t grow out normally after several months, or that develops the discolouration and texture changes listed above, warrants professional assessment.
Prevention: What Actually Works for Runners
Prevention requires consistent habits rather than any single intervention. These are the measures we recommend to our running patients.
Sock Selection
Avoid cotton socks for running. Cotton absorbs moisture and holds it against the skin. Merino wool or synthetic moisture-wicking materials draw sweat away from the foot. Thin, seamless socks that fit snugly reduce the friction that contributes to microtrauma.
Shoe Rotation
Alternate between at least two pairs of running shoes. A shoe needs 24 to 48 hours to dry fully between runs. If you run daily, a single pair never dries completely. Antifungal powder inside shoes during the drying period reduces fungal load further.
Post-Run Hygiene
Dry feet thoroughly after showering — including between the toes and around the nail folds — before putting on clean socks. At communal showers or change rooms, wear thongs or sandals on wet surfaces. These habits are particularly relevant for triathletes, who frequently change in transition zones and swim in shared facilities.
Antifungal Products
Antifungal sprays or powders applied to feet and the inside of shoes reduce fungal colonisation but do not treat established nail infections. They are useful as prevention and as adjuncts to treatment.
Footwear Fit
Running shoes should have a thumb’s width of space between your longest toe and the end of the shoe. Shoes that are too short, too narrow, or too loose at the heel all increase microtrauma. Our team provides footwear advice as part of podiatry consultations for runners concerned about ongoing nail problems.
Treatment While Still Training
One of the most common questions we hear from runners is whether they need to stop training during treatment. For most cases, the answer is no.
Fungal nail treatment options include topical antifungal lacquers (slow-acting but useful for mild cases), oral antifungal medications, and laser treatment. Laser is the most effective option for runners because it targets the fungus within the nail without systemic side effects and requires no downtime. You can run the day of your treatment.
Our fungal nail laser treatment uses targeted energy to reach the nail bed where the fungal organisms live. Multiple sessions are typically required, spaced several weeks apart. Results are visible as the new, healthy nail grows through over six to twelve months.
For runners already dealing with recurrent infections, our post on why toenail fungus keeps coming back is worth reading before starting any treatment — understanding why infections recur is essential for long-term resolution.
Australian Context: Heat, Humidity, and Health Fund Cover
Australian summers — particularly in Sydney — create conditions that favour fungal nail infections in ways that cooler climates don’t. Ambient temperatures above 25°C, combined with training in enclosed shoes, produce the heat and humidity that dermatophytes need to flourish. Runners training through December to February, or participating in events like the Sydney Running Festival, are at elevated risk during these months.
Podiatry consultations for fungal nail assessment and treatment are covered by most major private health funds under Extras cover. Medibank, BUPA, HCF, and NIB all provide rebates for podiatry under general treatment or foot care categories — the amount varies by your level of cover. Fungal nail laser treatment may attract a separate item and rebate; check your policy details before your appointment.
Medicare does not cover routine podiatry for fungal nail infections, but if you have a chronic condition managed under a GP’s Team Care Arrangement, you may be eligible for Medicare-subsidised podiatry visits (Enhanced Primary Care plan, item 10962). Speak with your GP if you’re unsure whether you qualify.
We treat runners and athletes for fungal nail infections across our five Sydney clinics: CBD, Mosman, Dee Why, Rose Bay, and North Ryde.
Frequently Asked Questions
Q: Can I keep running with toenail fungus?
A: In most cases, yes. Fungal nail infections are not acutely painful and don’t prevent training. You should keep feet clean and dry, use moisture-wicking socks, and seek treatment — but there is no medical reason to stop running. If a nail is significantly thickened or lifting, see a podiatrist to ensure it doesn’t become a source of pain on the run.
Q: Do runners get toenail fungus more often than other people?
A: Yes. Research consistently shows athletes — particularly runners, triathletes, and football players — have higher rates of onychomycosis than the general population. The combination of microtrauma, prolonged moisture, and exposure to communal surfaces accounts for this.
Q: What socks prevent toenail fungus for runners?
A: Moisture-wicking socks made from merino wool or synthetic fibres (polyester, nylon, CoolMax) are significantly better than cotton. They draw sweat away from the foot, reducing the humidity that enables fungal growth. Change socks after every run.
Q: How do I treat toenail fungus while still training?
A: Laser treatment is the most compatible option with an active training schedule. It requires no medication, no recovery time, and does not affect your ability to run. Topical treatments require daily application but don’t restrict activity. Oral antifungal medications are effective but require a prescription and liver function monitoring for extended courses — discuss this with your podiatrist or GP.
Q: Is there a difference between athlete’s foot and toenail fungus?
A: Yes. Athlete’s foot (tinea pedis) is a fungal infection of the skin, causing peeling, itching, and redness. Toenail fungus (onychomycosis) affects the nail plate itself — causing discolouration, thickening, and brittleness. The two conditions are related: untreated athlete’s foot often progresses to nail infection. Both require treatment, but different treatments apply to each.
See a Podiatrist Before the Next Season
Fungal nail infections don’t resolve without treatment, and they tend to worsen over training seasons. If you’ve noticed discolouration, thickening, or brittleness in one or more toenails, an assessment with a podiatrist will confirm whether the cause is fungal and identify the right treatment approach.
With over 20 years of experience treating Sydney’s runners and athletes, our team understands the demands of training and will work around your schedule. You don’t need a referral.
Book online at any of our five Sydney locations — CBD, Mosman, Dee Why, Rose Bay, or North Ryde — or ask us about our fungal nail assessment at your next appointment.
