Paronychia

BASICS

Definition: Superficial inflammation of the lateral/posterior nail folds around fingernail or toenail.
Acute: <6 weeks; usually bacterial (pain, erythema, swelling, may develop abscess).
Chronic: ≥6 weeks or recurrent episodes; chronic swelling, tenderness, nail dystrophy, cuticle elevation, often fungal (Candida).
Chemotherapy-Associated Paronychia (CAP): 4–8 weeks after starting chemo.
Epidemiology: One of the most common hand infections in the U.S. All ages, more common in females.

Acute: Mixed flora in 50%. Most common—Staphylococcus aureus, Streptococcus pyogenes; less often Pseudomonas or other Gram-negatives.
Chronic: Eczematous reaction with secondary Candida albicans (~95%); repeated wet exposure, irritant, or allergen.
Common Triggers:
Trauma (nail biting, manicures, ingrown nail, hangnail, thumb-sucking)
Frequent hand washing, water immersion
Immunosuppression, diabetes, drug-induced (EGFR inhibitors, chemo)
Progression: Infection starts at lateral nail fold, may progress to abscess, chronic cases develop nail fold fibrosis, nail dystrophy.

Acute: Direct trauma, ingrown nails, manicures, nail biting, thumb-sucking
Chronic: Frequent wet work (bartenders, nurses, dishwashers), eczema, DM, immunosuppression
Drugs: EGFR inhibitors, retinoids, chemo, antiretrovirals

Acute: Avoid nail trauma (biting, picking, hangnail manipulation), ingrown nails
Chronic: Avoid wet work, irritants, allergens. Wear gloves with cotton liner, keep nails short, moisturize after hand washing.

Acute: Rapid onset pain, swelling, erythema, tenderness (2–5 days after trauma)
Chronic: ≥6 weeks duration, swelling, boggy/tender nail folds, nail dystrophy

Acute: Red, warm, tender, tense nail fold ± abscess/fluctuance/purulence
Chronic: Swollen, boggy nail fold; absent cuticle; thickened/discolored nail plate (Beau lines), multiple digits may be involved
Green nail: Pseudomonas (chloronychia)
Complications: Abscess, granulation tissue, nail separation

Felon (pulp abscess), cellulitis, herpetic whitlow, eczema, psoriasis, onychomycosis, contact dermatitis, malignancy (rare)

Acute, no abscess: Warm soaks (10–15 min, several times/day), topical antibiotics (mupirocin, bacitracin)
Abscess: Incision and drainage (I&D) is key
Chronic: Keep hands dry, moisturizer after washing, avoid triggers

Acute, mild (no abscess):
Topical antibiotics: mupirocin, bacitracin, triple antibiotic ointment
Soaks (chlorhexidine or povidone-iodine)
Acute, not responding or severe:
Oral antibiotics:
- Dicloxacillin 250 mg QID
- Cephalexin 500 mg TID–QID
- If exposure to oral flora: Amoxicillin-clavulanate 875/125 mg BID
- MRSA risk: TMP/SMX 160/800 mg BID, doxycycline 100 mg BID, clindamycin 300–450 mg TID–QID
Abscess: I&D, antibiotics if cellulitis/extension
Chronic:
Topical steroids (betamethasone 0.05% BID 7–14 days)
Topical antifungal (clotrimazole, nystatin TID up to 30 days)
Calcineurin inhibitor (tacrolimus 0.1% ointment BID up to 21 days, more effective than steroids but costly)

Follow-up after I&D in 24–48h to ensure improvement
Chronic: Avoid repeated immersion, nail trauma, triggers; use moisturizer after handwashing
Good glucose control (if diabetic)
Avoid trimming cuticles, nail biting
Use gloves for wet work