What causes recurrent paronychial infections on my toenails?

Recurrent Paronychia of the Toenails: Causes and Management

Recurrent infections on the sides of toenails are most commonly caused by chronic paronychia, where the cuticle becomes detached from the nail plate, allowing microorganisms to enter the subcuticular space and cause inflammation and infection. 1

Etiology

Chronic paronychia of the toenails typically results from:

• Moisture exposure: Prolonged exposure to water causes swelling of the posterior nail fold and detachment of the cuticle from the nail plate, creating a water-tight seal breach 2, 1
• Microorganism entry: Once the cuticle barrier is compromised, both bacteria and fungi (particularly Candida species) can enter the subcuticular space 1
• Vicious cycle: This entry causes further cuticular detachment, perpetuating the condition 2

Common causative organisms:

• Fungi:
  • Candida species (particularly C. parapsilosis and C. guilliermondii) 1, 3
  • Dermatophytes (especially Trichophyton rubrum) 2, 3
• Bacteria:
  • Pseudomonas aeruginosa (causing green or black nail discoloration) 3
  • Staphylococcus aureus 3

Clinical Presentation

Chronic paronychia typically presents with:

• Swelling of the posterior and lateral nail folds 2, 1
• Tenderness and erythema around the nail 1
• White, green, or black discoloration in the proximal and lateral portions of the nail 1
• Transverse or longitudinal furrows or pitting of the nail plate 1
• Nail friability and potential detachment from the nail bed 1

Diagnostic Approach

Proper diagnosis is crucial before initiating treatment:

• Visual examination: Look for characteristic signs of paronychia versus onychomycosis 2
• Microbial testing: Bacterial cultures and fungal microscopy/cultures should be obtained if infection is suspected 2, 1
• Rule out other conditions: Psoriasis, lichen planus, and chronic nail eczema can mimic infectious nail disorders 4

Treatment Algorithm

1. Address Underlying Causes:

• Minimize moisture exposure to the feet 1
• Avoid trauma to the nail and surrounding tissue 1
• Wear appropriate footwear that doesn't compress toes 2

2. For Bacterial Paronychia:

• Topical antiseptics (octenidine) 3
• For Pseudomonas: Ciprofloxacin (oral or topical depending on severity) 3
• For other bacteria: Antibiotics based on culture results 3

3. For Fungal Paronychia:

• If limited to 1-2 nails with <50% involvement:

  • Topical antifungals: amorolfine or ciclopirox 3

• If extensive (>3 nails or >50% nail involvement):

  • For dermatophyte infections: Oral terbinafine 3
  • For Candida infections: Oral fluconazole 3, 5
  • Alternative: Oral itraconazole (200mg daily for 12 weeks continuously or as pulse therapy) 2

4. For Mixed or Chronic Paronychia:

• Combination therapy with:
  • Topical antifungals
  • Anti-inflammatory agents
  • Barrier protection 5

Prevention Strategies

• Keep nails short and properly trimmed 2
• Wear protective footwear in public areas (gyms, pools, hotel rooms) 2
• Use absorbent powders and antifungal powders in shoes 2
• Wear cotton, absorbent socks 2
• Avoid sharing nail clippers 2
• Consider treating or discarding contaminated footwear 2

Important Caveats

• Treatment failure is common (40-70% recurrence rate) and may require prolonged therapy 2
• Toenails grow slowly, requiring up to 12-18 months for complete regrowth 2
• Mechanical debridement may be necessary to remove infected material, particularly if dermatophytomas (dense white lesions of packed hyphae) are present 2
• All infected family members should be treated simultaneously to prevent reinfection 2

Remember that proper diagnosis with laboratory confirmation is essential before initiating treatment, as approximately 50% of nail dystrophies are fungal in origin, but the remainder may have other causes requiring different management approaches 2.