Paronychia

Paronychia is inflammation/infection of the nail folds (proximal, lateral, or both) of the fingers or toes, and is one of the most common hand infections seen in emergency and primary care settings. [1-2] It is classified as acute (<6 weeks, typically bacterial) or chronic (≥6 weeks, multifactorial irritant dermatitis). [1][3]

1. History

• Onset and duration: Acute (<6 weeks) vs. chronic (≥6 weeks) — this distinction drives management [1]
• Precipitating event: Nail biting, hangnail picking, manicure/pedicure, splinter, ingrown nail, cuticle trauma [2-3]
• Symptom characterization: Pain, swelling, erythema, warmth localized to the nail fold; ask about purulent drainage or fluctuance
• Timing: Rapid onset (hours to days) suggests acute bacterial; insidious onset over weeks suggests chronic or fungal [1]
• Occupational exposures: Prolonged wet work (dishwashers, bartenders, florists, bakers, swimmers) — key for chronic paronychia [1]
• Important negatives: No vesicular lesions (rules out herpetic whitlow), no volar pulp involvement (rules out felon), no pain with passive extension of the digit (rules out flexor tenosynovitis) [4-5]

2. Alarm Features

• Spreading cellulitis or lymphangitis/lymphadenopathy — signs of regional spread [6]
• Fusiform ("sausage") swelling of the digit with pain on passive extension → suspect pyogenic flexor tenosynovitis (Kanavel signs) — surgical emergency [4-5]
• Volar pulp involvement → suspect felon, which requires separate drainage approach [7]
• Failure to improve after adequate drainage and antibiotics → consider osteomyelitis of the distal phalanx, especially in diabetics [8]
• Systemic signs: Fever, rigors, sepsis — rare but mandate urgent escalation [6]
• Immunocompromised patients (diabetes, HIV, chemotherapy) — higher risk of rapid progression and atypical organisms [1]

3. Medications

• Medication contributors:
  • EGFR inhibitors (cetuximab, erlotinib, gefitinib) — well-known cause of drug-induced paronychia [9-10]
  • Retinoids (isotretinoin, acitretin), antiretrovirals (indinavir, lamivudine) [11]
• Common treatments:
  • Mild/early: Warm soaks ± Burow solution or 1% acetic acid, topical antibiotics (mupirocin) [1]
  • Moderate: Oral antibiotics — first-line: TMP-SMX or cephalexin for MSSA coverage; clindamycin if MRSA concern [1][4]
  • Chronic: Topical steroids (clobetasol) are more effective than systemic antifungals; topical antifungals as adjunct [3]
• Contraindicated: Avoid incision and drainage for herpetic whitlow (can cause viral dissemination and bacterial superinfection) [4]
• Caution: Oral antibiotics are usually unnecessary if adequate drainage is achieved, unless immunocompromised or severe infection [1]

4. Diet

• No specific dietary triggers for acute paronychia
• For chronic paronychia, minimize prolonged wet exposure during food preparation — wear cotton-lined gloves [1]
• Adequate nutrition and glycemic control in diabetics support wound healing

5. Review of Systems

• Constitutional: Fever, chills (suggests systemic spread)
• Skin: Other skin lesions, vesicles (herpetic whitlow), rashes (psoriasis, eczema — associated with chronic paronychia)
• MSK: Pain with finger flexion/extension, joint stiffness (tenosynovitis)
• Endocrine: Diabetes symptoms (polyuria, polydipsia) — risk factor for complicated infections
• Immune: HIV risk factors, immunosuppressive medications, recent chemotherapy [9]

6. Collateral History and Family History

• Occupational history is critical — wet work, chemical exposure, food handling [1]
• Habits: Nail biting (onychophagia), thumb/finger sucking (especially in children — 24% of antibiotic-resistant cases) [12]
• Family history: Psoriasis, eczema, autoimmune conditions (associated with chronic nail changes)
• Social context: Manicure/pedicure history, shared nail instruments (infection risk)

7. Risk Factors

• Nail trauma: Nail biting, hangnail picking, aggressive manicures — most common precipitant [2-3]
• Wet work/chemical exposure: Housekeepers, dishwashers, bartenders, florists, bakers, swimmers [1]
• Diabetes mellitus — impaired immune function and tissue perfusion [8]
• Immunosuppression: HIV, organ transplant, chemotherapy [1]
• Medications: EGFR inhibitors, retinoids [9-10]
• Ingrown nails (especially toes)
• Peripheral vascular disease

8. Differential Diagnosis

• Herpetic whitlow: Vesicular lesions, grouped on erythematous base; may have prodromal tingling; Tzanck smear shows multinucleated giant cells — do NOT incise [4][12]
• Felon: Infection of the volar pulp space (not the nail fold); tense, painful fingertip pad [5][7]
• Pyogenic flexor tenosynovitis: Kanavel signs (fusiform swelling, flexed posture, tenderness along tendon sheath, pain with passive extension) — surgical emergency [4]
• Subungual melanoma/SCC: Chronic, non-healing periungual lesion unresponsive to treatment — biopsy indicated [2]
• Psoriatic nail disease: Pitting, onycholysis, oil-drop sign
• Osteomyelitis of distal phalanx: Persistent pain despite treatment, fistulous tracts — especially in diabetics [8]
• Pemphigus vulgaris: Rare cause of antibiotic-resistant paronychia [12]
• Contact dermatitis: Chronic irritant exposure mimicking chronic paronychia

9. Past Medical History

• Diabetes — most important comorbidity increasing complication risk [8]
• Immunosuppression (HIV, transplant, chemotherapy)
• Previous episodes of paronychia — recurrence is common
• Peripheral vascular disease — impaired healing
• Dermatologic conditions: Psoriasis, eczema
• Current cancer treatment — EGFR inhibitors, taxanes [9-10]
• Tetanus immunization status — update if indicated [5]

10. Physical Exam

• Inspection: Erythema, swelling, and tenderness of the lateral or proximal nail fold; look for purulent drainage or fluctuance [1][3]
• Palpation: Gently press on the nail fold — fluctuance indicates abscess requiring drainage [1]
• Assess for "runaround" abscess: Infection extending from one nail fold to the other (eponychia) — may require more extensive drainage [7]
• Check volar pulp: If tense and tender → felon, not paronychia [7]
• Kanavel signs: Fusiform swelling, flexed posture, tenderness along flexor sheath, pain with passive extension → flexor tenosynovitis [4]
• Vesicles: Grouped vesicles suggest herpetic whitlow [4]
• Lymphadenopathy: Epitrochlear or axillary nodes suggest spreading infection [6]
• Nail changes (chronic): Thickening, ridging, discoloration, onycholysis [11]

11. Lab Studies

• Routine labs are generally NOT needed for uncomplicated paronychia [1]
• Wound culture: Obtain if abscess is drained, immunocompromised patient, or failure of empiric therapy — most common pathogen is S. aureus; polymicrobial infections are common [1][9]
• CBC, CRP: Consider if systemic signs (fever, lymphangitis) or concern for deep space infection [6]
• Glucose/HbA1c: If diabetes suspected or known — glycemic control affects healing
• Tzanck smear: If vesicles present — multinucleated giant cells confirm HSV (herpetic whitlow) [12]
• KOH prep/fungal culture: For chronic paronychia — Candida is the most common fungal pathogen [3]

12. Imaging

• First-line: X-ray of the digit — indicated if concern for foreign body, osteomyelitis, or fracture [6][8]
• Ultrasound: Point-of-care ultrasound can help identify and localize a small abscess when clinical exam is equivocal [7]
• MRI: Gold standard for suspected osteomyelitis — highest sensitivity; consider when paronychia fails to respond to appropriate treatment [8]
• Imaging is unnecessary for straightforward, uncomplicated acute paronychia [1]

13. Special Tests

• Digital block: Essential for adequate drainage — use a digital nerve block (ring block or single-injection volar technique) with lidocaine without epinephrine (though evidence supports epinephrine safety in digital blocks) [7]
• Tzanck smear: Useful for antibiotic-resistant paronychia — 93% had diagnostic cytologic findings in one series [12]
• Nail plate elevation: If pus is suspected beneath the nail plate, partial or complete nail removal may be needed for adequate drainage [1][7]
• Biopsy: For chronic, non-healing paronychia unresponsive to therapy — rule out malignancy (SCC, melanoma) [2]

14. ECG

• Not applicable for uncomplicated paronychia
• Consider ECG only if systemic sepsis is suspected (rare)

15. Assessment

Acute paronychia is a superficial infection of the nail fold, most commonly caused by S. aureus and polymicrobial flora, precipitated by disruption of the nail barrier. [1][11] Severity ranges from mild cellulitis to frank abscess formation. Chronic paronychia (≥6 weeks) is primarily an irritant dermatitis rather than a primary infection, though secondary colonization with Candida and bacteria is common. [1][3]

Key clinical pearls:

• The most common mistake is treating herpetic whitlow as bacterial paronychia — look for vesicles and avoid I&D [4][12]
• Chronic paronychia unresponsive to treatment should raise concern for malignancy or osteomyelitis [2][8]
• Drug-induced paronychia (EGFR inhibitors) may require partial matricectomy if unresponsive to conservative therapy by 3 months [10]

16. Treatment Plan

Acute Paronychia — Stepwise Approach

• Mild (no abscess): Warm soaks 3–4 times daily for 15 minutes ± Burow solution or 1% acetic acid; topical antibiotic (mupirocin) ± topical steroid [1][3]
• Moderate (early abscess/cellulitis): Add oral antibiotics — cephalexin 500 mg QID or TMP-SMX DS BID (if MRSA concern) for 5–7 days; continue warm soaks [1][4]
• Abscess present — I&D is mandatory: [1][7]
  • Perform digital block
  • Simple paronychia: Lift the nail fold off the nail plate using a #11 blade or 18-gauge needle along the nail fold — allow pus to drain
  • Eponychia/runaround abscess: Single or double incision technique along the nail margin [7]
  • Subungual extension: Partial or complete nail removal to allow drainage [1][7]
  • Pack loosely with iodoform gauze; remove packing in 24–48 hours
  • Oral antibiotics are usually not needed post-drainage unless immunocompromised or severe infection [1]

Chronic Paronychia

• Eliminate irritant exposure — avoid wet work, wear cotton-lined rubber gloves [1]
• Topical steroids (clobetasol) are first-line — more effective than systemic antifungals [3]
• Topical antifungal (clotrimazole, ketoconazole) as adjunct [3]
• Emollients to restore nail barrier [3]
• Refractory cases: Eponychial marsupialization or en bloc excision of the proximal nail fold; partial matricectomy for drug-induced cases [3][10]

17. Disposition

• Discharge: Vast majority — uncomplicated paronychia is managed outpatient [1][7]
• Observation/Admission criteria:
  • Systemic signs of infection (fever, sepsis)
  • Suspected deep space infection or flexor tenosynovitis → urgent hand surgery consult [4]
  • Immunocompromised with rapidly progressing infection
  • Failed outpatient management with worsening despite I&D and antibiotics
• Specialist consultation triggers:
  • Hand surgery: Deep space infection, tenosynovitis, osteomyelitis [4][6]
  • Dermatology: Chronic paronychia unresponsive to treatment, suspected malignancy [2]
  • Oncology coordination: Drug-induced paronychia affecting cancer treatment [10]

18. Follow Up / Return Precautions

• Follow-up: 48 hours for wound check and packing removal after I&D; 1 week for reassessment [1]
• Return immediately for:
  • Worsening redness, swelling, or pain despite treatment
  • Red streaking up the hand/arm (lymphangitis)
  • Fever or chills
  • Inability to bend or straighten the finger (concern for tenosynovitis)
  • Numbness or color change in the fingertip
• Patient counseling:
  • Avoid nail biting, aggressive manicures, and cuticle manipulation [1][3]
  • Keep hands dry; use gloves for wet work [1]
  • Complete full antibiotic course if prescribed
• Expected recovery: Acute paronychia typically resolves within 5–10 days with appropriate treatment; chronic paronychia may take weeks to months [1]
• Tetanus prophylaxis: Update if not current and wound is at risk [5]

References

1. Acute and Chronic Paronychia. — Leggit JC. American Family Physician. 2017.

2. Acute and Chronic Paronychia. — Rockwell PG. American Family Physician. 2001.

3. Acute and Chronic Paronychia. — Rigopoulos D, Larios G, Gregoriou S, Alevizos A. American Family Physician. 2008.

4. Acute Hand Infections. — Rerucha CM, Ewing JT, Oppenlander KE, Cowan WC. American Family Physician. 2019.

5. Common Acute Hand Infections. — Clark DC. American Family Physician. 2003.

6. Diagnosis and Management of Upper Limb Soft Tissue Infections. — Auquit-Auckbur I, Beccari R, Coquerel-Beghin D, Garcia-Doldan CM. Orthopaedics & Traumatology, Surgery & Research : OTSR. 2025.

7. Management of Finger Felons and Paronychia: A Narrative Review. — Gottlieb M, Long B. The Journal of Emergency Medicine. 2025.

8. Osteomyelitis Mimicking Chronic Paronychia. — Signoret-Bravo MT, Berumen-Glinz C, Gatica-Torres M, Michel-Izeta BE, Domínguez-Cherit J. JAMA Dermatology. 2026.

9. Nail Toxicities Induced by Systemic Anticancer Treatments. — Robert C, Sibaud V, Mateus C, et al. The Lancet. Oncology. 2015.

10. Surgical Intervention for Paronychia Induced by Targeted Anticancer Therapies. — Hanania HL, Pacha O, Heberton M, Patel AB. Dermatologic Surgery : Official Publication for American Society for Dermatologic Surgery. 2021.

11. Acute and Chronic Paronychia of the Hand. — Shafritz AB, Coppage JM. The Journal of the American Academy of Orthopaedic Surgeons. 2014.

12. Clinical and Cytologic Features of Antibiotic-Resistant Acute Paronychia. — Durdu M, Ruocco V. Journal of the American Academy of Dermatology. 2014.