Acute Ingrown Toenail Infection

An ingrown toenail (onychocryptosis) occurs when the lateral nail edge penetrates the lateral nail fold, causing inflammation, granulation tissue and sometimes acute paronychia with abscess. It most often affects the great toe.

• Causes: incorrect nail cutting (curved or too short), tight footwear, trauma, hyperhidrosis, nail deformity (pincer nail), obesity, onychomycosis, adolescent growth.
• Staphylococcus aureus is the commonest pathogen; streptococci, anaerobes and Pseudomonas also occur.

Pain, redness, swelling of the lateral nail fold with purulent discharge and hypertrophic granulation tissue, worse on walking in shoes.

• Staging: mild erythema and swelling; abscess and drainage; hypergranulation and chronic.
• Differential diagnosis: acute bacterial paronychia, herpetic whitlow, tinea unguium, subungual exostosis, pyogenic granuloma, squamous cell carcinoma, glomus tumour, gout, osteomyelitis.
• Complications: abscess, cellulitis, osteomyelitis of the distal phalanx, chronic recurrence, nail deformity, foot ulcer and limb threatening infection in diabetes.

Clinical.

• Swab pus for culture in resistant or recurrent disease.
• Glucose, ankle brachial index or pulses assessment, neurological foot examination in diabetes.
• Plain radiograph if bone involvement is suspected (deep pain, exposed bone, chronic infection).
• Biopsy of non healing granulation to exclude malignancy.

Relieve pressure on the nail fold, treat infection and drain pus; perform partial avulsion for recurrent or severe disease.

• Supportive: warm soaks in salt water or dilute povidone iodine 10 minutes two to three times daily, elevate the foot, wear open toed shoes or sandals, cut nails straight across, avoid picking, check tetanus status.
• Pharmacological: topical fusidic acid 2 percent cream or mupirocin 2 percent ointment three times daily for 7 days for mild disease; oral flucloxacillin 500 mg four times daily for 7 days for cellulitis or abscess (children 25 mg/kg/day in four divided doses); clindamycin 300 mg four times daily if penicillin allergic; analgesia with paracetamol 1 g four times daily or ibuprofen 400 mg three times daily. Tetanus toxoid 0.5 mL IM if immunisation is out of date.
• Procedures: digital block with lidocaine 1 percent plain 3 to 5 mL (without adrenaline), then lift the nail edge and place a wisp of cotton, dental floss or a gutter splint under it; incision and drainage of abscess; partial nail avulsion with chemical matricectomy (phenol 88 percent applied for three 30 second applications) or surgical wedge resection for recurrent disease; total avulsion if severely deformed.
• Special groups: diabetes or peripheral vascular disease, early podiatry and surgery review and low threshold for antibiotics, IV if systemic; pregnancy, flucloxacillin, avoid phenol if large exposure; children, conservative splinting before ablation; anticoagulated patients, check international normalised ratio before surgery.
• Red flags: spreading cellulitis, fever, red streaking, exposed bone, non healing wound, diabetes with foot infection, pulseless toe.
• Follow-up: review in 48 to 72 hours after procedure and at 1 to 2 weeks; recurrence advice on correct nail trimming and footwear.