Key Takeaways
Onychomycosis — commonly known as nail fungus — is a chronic infection of the nail bed caused by dermatophytes, yeasts, or molds. It affects roughly 10% of adults globally and up to 50% of people over 70[1]. The good news: with the right treatment and consistent home care, the vast majority of cases resolve within a year.
Treat both feet, even if only one shows symptoms. Asymptomatic carriage is common and is the #1 reason fungus comes back after treatment.Pro tip
What is nail fungus?
Nail fungus is an infection that lives beneath the nail plate — in the nail bed and the matrix where new nail grows. This is why surface treatments (filing, polishing, scrubbing) cannot reach or eliminate the infection on their own.
The most common pathogen is Trichophyton rubrum, the same dermatophyte responsible for athlete's foot. In fact, untreated athlete's foot is the leading source of toenail fungus[2].
What causes nail fungus
Fungi thrive in warm, dark, moist environments — exactly the climate inside a closed shoe. The most common entry points are:
- Microscopic cracks in the nail or surrounding skin
- Trauma to the nail (stubbing, ill-fitting shoes, sports)
- Walking barefoot in humid shared spaces (pools, locker rooms, hotel showers)
- Improperly disinfected pedicure tools or footbaths
Most patients I see have been treating the surface for months without realizing the infection lives underneath the nail.
— Dr. Maria de Vries, MD
Symptoms to watch for
Early-stage onychomycosis is easy to miss. Look for:
- White, yellow, or brown discoloration starting at the nail tip
- Thickening or distortion of the nail shape
- Brittle, crumbly edges
- A subtle, musty odor
- Detachment of the nail from the nail bed (onycholysis)
Do not file the nail aggressively or remove cuticles. This creates entry points for secondary bacterial infection — a serious complication, especially for people with diabetes.Important
Stages of progression
| Stage | Appearance | Recommended action |
|---|---|---|
| Early | Small white/yellow spot at nail tip | Topical treatment + hygiene |
| Moderate | Discoloration covers ⅓–½ of nail, thickening | Topical + filing + medical review |
| Advanced | Full nail involvement, separation, pain | See a dermatologist |
How to treat nail fungus
Treatment depends on severity, but the principle is the same: deliver an antifungal agent to the nail bed and keep the area dry and clean long enough for healthy nail to grow out.
Quick definition
1. Topical antifungal treatment
Topical sprays and lacquers containing actives like clotrimazole, terbinafine, or amorolfine are the first line of defense for mild to moderate cases. Apply daily, consistently, for the full duration recommended on the label.
Anti-Fungal Shoe Disinfectant Spray