Understanding Toenail Fungus

Onychomycosis—fungal infection of the toenails—is one of the most common nail disorders, affecting an estimated 10% of the general population and up to 50% of people over 70. It is caused by dermatophyte fungi (most commonly Trichophyton rubrum), yeasts (Candida species), or non-dermatophyte molds—organisms that thrive in the warm, moist environment of shoes and nail beds. Despite being extremely common, onychomycosis is often underdiagnosed or incorrectly attributed to other conditions, and it is frequently undertreated because patients and providers underestimate the persistence required for successful treatment.

Recognizing Toenail Fungus

Onychomycosis presents with nail changes that include thickening and brittleness, yellow, brown, or white discoloration (particularly starting at the tip or lateral edges), separation of the nail from the nail bed (onycholysis), accumulation of chalky debris under the nail, and distortion of nail shape. The great toenail is most commonly affected, but any toenail can be involved. Conditions that can mimic onychomycosis include nail psoriasis, traumatic nail changes, and bacterial infections—which is why laboratory confirmation before expensive treatment is valuable.

Confirming the Diagnosis

Clinical diagnosis of onychomycosis is correct approximately 50–60% of the time without laboratory testing. Before committing to months of treatment—particularly oral antifungal medications with systemic effects—laboratory confirmation is valuable. Options include periodic acid-Schiff (PAS) staining of nail clippings (most sensitive), fungal culture (most specific but slow), and in-office fluorescence microscopy (potassium hydroxide preparation). Confirming the diagnosis ensures treatment is directed at an actual fungal infection rather than a mimicking condition and identifies the specific organism to guide antifungal selection.

Treatment Options: What Actually Works

Oral Antifungals (Most Effective)

Terbinafine (Lamisil) is the most effective oral antifungal for dermatophyte onychomycosis, with mycologic cure rates of 70–80% and complete cure rates of 35–55%. It is taken daily for 6 weeks (fingernails) or 12 weeks (toenails). Liver function monitoring is recommended for patients with hepatic risk factors. Itraconazole (Sporanox) is an alternative, particularly for non-dermatophyte or Candida infections, given in pulse dosing regimens. Oral antifungals are contraindicated in patients with significant liver disease and require consideration of drug interactions.

Topical Antifungals (Convenient but Less Effective)

Efinaconazole (Jublia) and tavaborole (Kerydin) are prescription topical solutions with FDA approval for onychomycosis. Applied daily for 48 weeks, they achieve complete cure rates of approximately 15–20%—substantially lower than oral therapy but appropriate for patients who cannot take or prefer to avoid systemic medication. Over-the-counter topicals (tea tree oil, ciclopirox nail lacquer) have limited evidence and are generally insufficient for established infection.

Laser Treatment

Nd:YAG and diode laser treatments are FDA-approved devices for onychomycosis. They work by selectively heating fungal elements within the nail unit. Clinical studies show variable results, with complete cure rates generally lower than oral terbinafine but without systemic medication risks. Laser is an option for patients who cannot take oral antifungals or who prefer an in-office treatment approach. Multiple sessions are typically required.

Prevention of Recurrence

Onychomycosis recurrence rates are high—approximately 25% within 5 years of successful treatment—because the environmental conditions that caused the initial infection persist. Prevention includes wearing moisture-wicking socks and breathable footwear, using antifungal spray in shoes weekly, wearing sandals or shower shoes in shared facilities, and treating tinea pedis (athlete’s foot) promptly since it frequently precedes onychomycosis. Maintaining clean, trimmed nails and controlling predisposing conditions (diabetes, immunosuppression) reduces recurrence risk.

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Dr. Tom Biernacki, DPM is a double board-certified podiatrist and foot & ankle surgeon at Balance Foot & Ankle Specialists in Southeast Michigan. With over a decade of clinical experience, he specializes in heel pain, bunions, diabetic foot care, sports injuries, and minimally invasive surgery. Dr. Biernacki is a member of the APMA and ACFAS, and his patient education content on MichiganFootDoctors.com and YouTube has reached over one million views.