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Toenail Pus: Causes, Diagnosis, and Treatment of Paronychia & Onychomycosis

Pus beneath or around the toenail signals infection—most commonly paronychia (periungual soft tissue) or onychomycosis (fungal nail) with secondary bacterial infection.

Common Causes

Diagnosis

Clinical: inspection, palpation, expressibility of pus
Gram stain/culture if severe, recurrent, or immunocompromised
KOH prep / fungal culture / PAS stain for onychomycosis
X-ray if osteomyelitis suspected (diabetic foot)

Treatment

Acute paronychia: Warm soaks 3–4×/day; topical antibiotic (mupirocin) ± oral (cephalexin, dicloxacillin) if spreading. Incision & drainage if abscess.
Chronic paronychia: Avoid moisture, topical antifungal + steroid (e.g., clotrimazole/betamethasone), systemic antifungal if Candida dominant.
Onychomycosis: Oral terbinafine/itraconazole (pulse or continuous) + topical (ciclopirox, tavaborole, efinaconazole). Nail debridement.
Ingrown nail: Partial nail avulsion + phenol matrixectomy (definitive).

Red Flags → Urgent Referral

Diabetes/PVD/immunosuppression + spreading cellulitis
Deep space infection (felon, osteomyelitis)
Sepsis signs

Prompt treatment prevents complications and nail loss.

Dog Bites - Related Articles

Cause	Features	Risk Factors
Acute bacterial paronychia	Rapid onset, erythema, swelling, throbbing pain, pus at nail fold	Trauma (hangnail, manicure), ingrown nail, nail biting, diabetes
Chronic paronychia	>6 weeks, recurrent, cuticle loss, nail dystrophy; mixed flora (Candida + bacteria)	Wet work, immunosuppression, diabetes, atopic dermatitis
Onychomycosis + secondary infection	Thick, yellow, crumbly nail; subungual debris; pus if bacterial superinfection	Age, tinea pedis, trauma, occlusive shoes, PVD, immunosuppression
Ingrown toenail (onychocryptosis)	Lateral nail plate penetrates fold → inflammation, granulation, pus	Improper trimming, tight shoes, hyperhidrosis, congenital nail shape