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InfectiousICD-10: B35.1Affects approximately 10% of the general population and up to 50% of people over 70

Fungal Nail Infection (Onychomycosis)

Also known as: Onychomycosis, Toenail Fungus, Nail Fungus, Tinea Unguium

Fungal nail infection, medically known as onychomycosis, is a common condition caused by dermatophytes, yeasts, or molds that invade the nail bed, causing the nail to become thickened, discolored, and brittle. The condition most frequently affects toenails due to the warm, moist environment inside shoes, and it tends to worsen slowly over time without treatment. Although not usually painful in early stages, advanced infections can cause discomfort while walking and may spread to other nails or the surrounding skin.

Symptoms

Thickened, distorted nails
Yellow, brown, or white discoloration of the nail
Brittle, crumbly, or ragged nail edges
Separation of the nail from the nail bed (onycholysis)
Foul smell from the affected nail
Debris buildup under the nail
Pain or discomfort when wearing shoes or walking (advanced cases)

Causes

  • Dermatophyte fungi (Trichophyton rubrum, T. mentagrophytes) as the most common cause
  • Yeast infections (Candida species), more common in fingernails
  • Non-dermatophyte molds in tropical and subtropical climates
  • Spread from athlete's foot (tinea pedis) to the toenails

Risk Factors

  • Age over 60 due to slower nail growth and reduced blood circulation
  • Diabetes or peripheral vascular disease
  • Weakened immune system
  • Walking barefoot in communal areas like gyms, pools, and locker rooms
  • Wearing occlusive, non-breathable footwear
  • History of athlete's foot
  • Nail trauma or injury

Diagnosis

  • Visual examination of nail changes
  • Nail clipping or scraping sent for KOH preparation and microscopy
  • Fungal culture to identify the specific organism
  • PCR testing for rapid and accurate species identification

Treatment

  • Oral antifungal medications (terbinafine, itraconazole) as first-line treatment
  • Topical antifungal lacquers (ciclopirox, efinaconazole) for mild cases
  • Combination of oral and topical antifungal therapy
  • Laser therapy for treatment-resistant infections
  • Surgical or chemical nail removal in severe cases
  • Treatment of concurrent athlete's foot to prevent reinfection

Prevention

  • Keep feet clean and dry, especially between the toes
  • Wear breathable shoes and moisture-wicking socks
  • Wear protective footwear in communal showers, pools, and gyms
  • Trim nails straight across and keep them at a moderate length
  • Disinfect nail clippers and avoid sharing nail care tools
  • Treat athlete's foot promptly to prevent spread to nails

When to See a Doctor

  • Nail discoloration or thickening is worsening despite home care
  • You have diabetes and notice changes in your toenails
  • The infected nail is causing pain or difficulty walking
  • The infection appears to be spreading to other nails or skin

Frequently Asked Questions

Related Conditions

Eczema

Dermatological

Psoriasis

Dermatological

Type 2 Diabetes

Endocrine

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