Toenail Splitting (Onychoschizia): Causes, Prevention, and Treatment

Onychoschizia (horizontal nail plate splitting) has multiple etiologies:

Common Causes

• Trauma: Repetitive microtrauma (tight shoes, running), acute injury.
• Fungal Infection (Onychomycosis): Thickened, discolored, brittle nails; confirmed by KOH prep/PAS/culture.
• Psoriasis: Pitting, onycholysis, subungual hyperkeratosis, oil spots.
• Eczema/Dermatitis: Periungual inflammation → nail dystrophy.
• Systemic Disease: Diabetes (vascular/neuropathic), thyroid disorders, iron deficiency, Raynaud’s.
• Nutritional Deficiencies: Iron, zinc, biotin, protein.
• Medications: Chemotherapy (taxanes), retinoids, EGFR inhibitors.
• Aging: Reduced nail matrix turnover, decreased lipid content → brittleness.

Prevention

• Keep nails trimmed short, file gently in one direction.
• Wear properly fitted shoes; moisture‑wicking socks.
• Gloves for wet work; avoid harsh chemicals.
• Moisturize nails/cuticles daily (urea/lactic acid creams).
• Balanced diet; supplement only if deficiency confirmed.

Treatment

• Address underlying cause (antifungal for onychomycosis, systemic therapy for psoriasis).
• Topical nail strengtheners (hydroxypropyl chitosan, silanediol salicylate).
• Biotin 2.5 mg/day if deficient (3–6 months for effect).
• Avoid acrylic/gel nails during recovery.

See a dermatologist if splitting persists >3 months despite care, or if associated with discoloration, thickening, pain, or systemic symptoms.