Paronychia and finger infections
Red swollen nail fold with pus: lift the fold and let it out. A swollen, bent, painful whole finger is a flexor sheath infection — surgery today.
A 30-year-old cook has a red, throbbing swelling at the side of her index fingernail for 2 days, with a yellow area under the skin.
A 50-year-old diabetic gardener has a swollen, flexed ring finger. Straightening it is very painful, and the whole finger is tender along the palm side.
Which one can you drain here, and which needs the hand surgeons tonight?
- Find the spaceNail fold (paronychia), pulp (felon), tendon sheath, palm.
- Kanavel signsFlexed finger, fusiform swelling, tenderness along the sheath, pain on passive extension: hand surgeons now.
- Paronychia without pusWarm soaks 3–4 times a day, elevation, antibiotics if spreading.
- Paronychia with pusDrain: lift the nail fold with a blade, digital block.
- FelonDrain by an experienced doctor, avoid the pad and the sides where nerves run.
- After drainageWarm soaks, dressing, review at 48 hours.
- Chronic paronychiaKeep hands dry, treat for candida, stop wet work.
- Kanavel signs (flexor sheath infection)
- Spreading to the palm or forearm
- Diabetic or immunosuppressed with severe infection
- Bone involvement (osteomyelitis)
- Not improving after 48 hours
- Flexor tenosynovitis
- Herpetic whitlow (don't incise)
- Retained foreign body
- Osteomyelitis
- Melanoma under the nail mimicking infection
| Acute paronychia | Under 6 weeks, usually Staph aureus |
| Chronic paronychia | Over 6 weeks, wet work, candida |
| Digital block | Lidocaine 1% plain, 2–3 mL each side of the finger base |
| Flucloxacillin | 500 mg every 6 hours for 5–7 days |
| Warm soaks | 10–15 minutes, 3–4 times a day |
Check every dose against a current drug reference and your hospital protocol.
On this page
Types
| Infection | Where | Features |
|---|---|---|
| Acute paronychia | Nail fold | Red, swollen, pus at the side of the nail |
| Chronic paronychia | Nail fold, several fingers | Swelling, lost cuticle, wet-work, candida |
| Felon (pulp space) | Finger pad | Tense, very painful pad |
| Herpetic whitlow | Fingertip | Vesicles, healthcare workers, children with cold sores |
| Flexor tenosynovitis | Tendon sheath | Kanavel signs |
Management
Warm soaks, elevation, antibiotics if spreading
Drain under digital block
Felon: drain (experienced), antibiotics
- Herpetic whitlow: don't incise
- aciclovir if early
Hand surgeons, IV antibiotics
Draining a paronychia
- Digital blockPlain lidocaine 1%, 2–3 mL each side of the base of the finger.
- Lift the nail foldSlide a blade (flat side to the nail) under the fold at the point of the pus, away from the nail bed.
- Release pusSwab for culture if severe or recurrent.
- Under the nailIf pus is under the nail, remove part of the nail.
- Dress and soakWarm soaks from the next day.
Investigations
| Test | Why |
|---|---|
| Pus swab | Severe, recurrent, diabetic |
| X-ray | Foreign body, bone involvement |
| Blood glucose | Recurrent or severe infection |
| FBC, CRP | Spreading infection |
Treatment
Common mistakes
- Missing flexor tenosynovitis.
- Incising a herpetic whitlow.
- Giving antibiotics alone for a collection of pus.
- Cutting into the nail bed.
- Forgetting blood glucose in recurrent infections.
Frequently asked questions
How is acute paronychia treated?
Warm soaks and elevation if there is no pus; drainage under digital block if there is pus. Antibiotics if infection is spreading.
What are Kanavel's signs?
A flexed finger, fusiform swelling, tenderness along the flexor sheath and pain on passive extension. They suggest flexor tendon sheath infection.
Should a herpetic whitlow be incised?
No. It is viral; incision can spread infection.
What causes chronic paronychia?
Repeated wet work and irritants, often with candida.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. A finger is held slightly bent, swollen along its length, and painful on passive extension. What is it?
Answer: Sheath infection. Kanavel's signs: hand surgery urgently.
- Gout: No.
- Paronychia: Nail fold only.
- Felon: Pulp only.
- Herpetic whitlow: Vesicles.
2. A health worker has painful clear vesicles on a fingertip. What should be avoided?
Answer: Incision. Herpetic whitlow shouldn't be incised.
- Covering the finger: Fine.
- Avoiding contact: Fine.
- Analgesia: Fine.
- Antivirals: Can be used.
3. What is the treatment of an acute paronychia with pus?
Answer: Drainage. Lift the nail fold or incise under a ring block.
- Steroid cream: No.
- Oral antibiotics alone: Pus needs drainage.
- Nail removal for all: Not first.
- Antifungal cream: Chronic paronychia.
4. Three days after a thorn prick, a farmer’s index finger is uniformly swollen and held slightly bent. There is tenderness along the palm side of the finger and severe pain when the finger is passively straightened. What is the diagnosis?
Answer: Flexor sheath infection. Kanavel’s four signs of flexor tenosynovitis: fusiform (sausage) swelling, finger held in slight flexion, tenderness along the flexor sheath, and pain on passive extension. Pus in the closed sheath can rapidly destroy the tendon, so urgent surgical washout and IV antibiotics are needed. Delay risks a stiff, useless finger.
- Paronychia — drainage: Paronychia is an infection at the nail fold, not along the whole flexor surface of the finger.
- Felon — pulp drainage: A felon is an abscess in the fingertip pulp, not a uniformly swollen finger with pain on extension.
- Gout — NSAIDs: These are Kanavel signs of flexor sheath infection after a thorn prick; gout does not follow a penetrating injury.
5. A man has a red, swollen finger held in flexion, with tenderness along the flexor sheath and pain on passive extension after a thorn prick. What is the diagnosis?
Answer: Flexor tenosynovitis. Kanavel signs of flexor sheath infection: finger held in flexion, fusiform swelling, tenderness along the flexor sheath, and pain on passive extension (most sensitive). Needs urgent IV antibiotics, elevation and surgical washout of the sheath to prevent tendon necrosis and adhesions. Paronychia: nail fold (drain). Felon: pulp space abscess (drain).
- Paronychia: Paronychia affects the nail fold.
- Felon: A felon affects the pulp space.
- Cellulitis alone: Cellulitis alone does not give Kanavel signs.
6. A man has an abscess in the pulp of his index fingertip, with throbbing pain and swelling. What anatomical feature makes it so painful?
Answer: Fibrous septa create closed compartments. A felon (pulp space infection) is painful because fibrous septa run from the skin to the periosteum of the distal phalanx, dividing the pulp into many small closed compartments. Swelling raises pressure quickly, causing severe throbbing pain and risking thrombosis of the vessels to the diaphysis of the distal phalanx and osteomyelitis. It is drained through a lateral or midline incision.
- The pulp lacks any nerve supply: The pulp is richly innervated.
- The flexor tendon sheath is absent here: Sheath ends at the distal phalanx base, not relevant.
- Skin there is very thin and loose: Pulp skin is thick and firmly attached.
- The digital artery runs superficially: Not the reason.
7. Infection in the flexor sheath of the little finger can spread to which space?
Answer: Ulnar bursa. The flexor sheath of the little finger is usually continuous with the ulnar bursa, which encloses the long flexor tendons in the carpal tunnel. The thumb sheath is continuous with the radial bursa (around FPL). The two bursae often communicate at the wrist, so infection can spread from the little finger to the thumb (horseshoe abscess) and into the forearm (Parona space).
- Thenar space: Linked with the index finger.
- Radial bursa only: Thumb, not little finger.
- Midpalmar space only through the index: Not the route.
- Dorsal subaponeurotic space: Not the usual route.
References and dose sources
- NICE CKS — Paronychia (acute)
- Lidocaine (lignocaine) dosing: Drugs.com: Lidocaine dosage (see also our lidocaine (lignocaine) dose page)
- Flucloxacillin dosing: Drugs.com: Flucloxacillin (international) (see also our flucloxacillin dose page)
- Clindamycin dosing: Drugs.com: Clindamycin dosage (see also our clindamycin dose page)
- Co-amoxiclav (amoxicillin with clavulanic acid) dosing: Drugs.com: Amoxicillin/clavulanate dosage (see also our co-amoxiclav (amoxicillin with clavulanic acid) dose page)
- Aciclovir dosing: Drugs.com: Acyclovir (aciclovir) dosage (see also our aciclovir dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.