Hand infections (paronychia, felon, flexor tenosynovitis) !

Hand infections range from a red, sore nail fold to pus in a tendon sheath that can destroy a finger. Deep infections need urgent surgery.

Updated 2026-11-01

Structures involved

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Why it happens

Patterns of acute inflammation: serous, fibrinous, purulent, abscess, ulcer

What it is

Bacterial (and sometimes viral or fungal) infections of the hand's closed spaces. The classic exam entities are paronychia (infection of the nail fold), felon (abscess of the fingertip pulp), herpetic whitlow (viral infection of the fingertip), pyogenic flexor tenosynovitis (pus inside a flexor tendon sheath) and deep space infections, including bite wounds. The hand's compartments are tight and close to tendons, bones and joints, so delay can cost function.

Who gets it

Hand infections are very common in emergency and primary care. Paronychia is the most frequent; pyogenic flexor tenosynovitis accounts for a small share of acute hand infections but carries the most risk. Manual workers, farmers and people with diabetes are often affected, and in Colombia agricultural and occupational puncture wounds and animal bites are common entry routes.

Causes

Staphylococcus aureus (including methicillin-resistant strains) and streptococci in most cases
Candida and other fungi in chronic paronychia
Herpes simplex virus in herpetic whitlow
Mixed mouth flora such as Eikenella corrodens after human bites and fist-fight injuries; Pasteurella multocida after cat and dog bites
Neisseria gonorrhoeae in disseminated gonococcal tenosynovitis
Entry through hangnails, nail biting, manicures, splinters, needle sticks and penetrating injuries

Risk factors

Diabetes mellitus
Immunosuppression, kidney failure and peripheral vascular disease
Frequent hand immersion in water (dishwashers, cleaners)
Nail biting and cuticle trimming
Penetrating trauma, bites and injection drug use

Pathophysiology

Bacteria enter through a break in the skin and multiply in a confined space. In a felon, fibrous septa that anchor the pulp skin to the distal phalanx create small compartments, so pus raises pressure, causes throbbing pain and can lead to necrosis or osteomyelitis. The flexor tendon sheath is a closed synovial tube; once infected, swelling and pus raise the pressure, impair the tendon's blood supply and can spread proximally to the palm and the forearm, and later cause adhesions or tendon necrosis.

Classification

Acute paronychia (bacterial, sudden) versus chronic paronychia (more than six weeks, often fungal or irritant)
Felon: pulp space abscess of the distal phalanx
Herpetic whitlow: viral vesicles on the fingertip, not to be incised
Pyogenic flexor tenosynovitis: infection of the flexor tendon sheath
Deep space infections: thenar, midpalmar and web-space (collar-button) abscesses; septic arthritis and osteomyelitis of the hand
Bite wounds: human (including clenched-fist injury) and animal

Symptoms and signs

Red, swollen, painful skin around the nail with pus under the fold (paronychia)
Tense, throbbing, very painful fingertip pulp (felon)
Grouped painful vesicles on the finger, often with burning beforehand (herpetic whitlow)
Swollen, tender finger held slightly bent and painful to straighten (flexor tenosynovitis)
Fever, red streaks up the arm and swollen axillary nodes in spreading infection

Diagnosis

Clinical: Diagnosis is mainly clinical: location of swelling, fluctuance, Kanavel signs, range of motion, a careful history of bites, punctures and occupation, and a sensory and vascular examination of the finger.
Tests: Culture of pus from any drainage. White cell count, ESR and CRP support deep infection but a normal result does not exclude it. Viral PCR or Tzanck test for suspected herpetic whitlow; blood glucose in all patients.
Imaging: Radiographs for foreign bodies, gas, fractures (fight bites) and osteomyelitis. Ultrasound can show fluid in the tendon sheath or an abscess; MRI for unclear deep infection or osteomyelitis.

Differential diagnosis

Herpetic whitlow (viral, must not be incised)
Cellulitis without an abscess
Gout or pseudogout of a finger joint
Trigger finger or inflammatory tenosynovitis
Retained foreign body reaction

Goal of treatment

Drain pus and control infection early enough to preserve tendon gliding, finger movement and sensation.

Treatment

Conservative: Early acute paronychia without pus: warm soaks several times a day, elevation and, when cellulitis is present, oral antibiotics active against staphylococci and streptococci.
Procedure: Paronychia or felon with an abscess: incision and drainage under digital block, avoiding the pad of the finger and the neurovascular bundles; partial nail removal when pus lies under the nail.
Medical: Antibiotics guided by the setting: anti-staphylococcal agents for most infections, coverage for mouth flora (for example a beta-lactam with a beta-lactamase inhibitor) for bites, and antivirals for herpetic whitlow.
Surgical: Pyogenic flexor tenosynovitis: hand surgery referral, intravenous antibiotics, splinting and elevation; if not improving quickly or seen late, open or closed irrigation of the tendon sheath. Deep space abscesses and fight bites need surgical exploration and washout.
Follow-up: Nursing priorities: elevate the hand above heart level, check finger colour and capillary refill, record the spread of redness, assess pain, control blood glucose, and give tetanus prophylaxis; teach wound care after drainage.
Rehabilitation: Early hand therapy and active movement after deep infections to limit tendon adhesions and stiffness.

Complications

Tendon adhesions, stiffness and loss of finger movement
Tendon necrosis or rupture
Osteomyelitis of the distal phalanx and septic arthritis
Spread to the palm and forearm (horseshoe abscess)
Chronic nail deformity
Amputation of the finger, especially with diabetes and late treatment

Prognosis

Superficial infections such as paronychia heal well with drainage and care. Flexor tenosynovitis leaves some stiffness in a sizeable minority even with prompt treatment; delay, diabetes, ischaemia, renal failure and older age raise the risk of amputation.

Prevention

Avoid biting nails and cutting cuticles
Wear gloves for wet work and when handling soil and animals
Clean and seek care early for puncture wounds and bites
Good glucose control in diabetes

Test yourself

Think of the answer, then tap the question to see it.

What are Kanavel's four signs of pyogenic flexor tenosynovitis?

Fusiform swelling, finger held in flexion, tenderness along the flexor sheath and pain on passive extension (often the earliest sign).

What is a felon?

An abscess of the closed fibrous compartments of the fingertip pulp.

Why should a herpetic whitlow not be incised?

It is a viral infection; incision does not help and risks bacterial superinfection and spread.

Which organism is classically linked to human bite and clenched-fist injuries?

Eikenella corrodens, together with other mouth flora.

Which organism is classically linked to cat and dog bite infections?

Pasteurella multocida.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Pyogenic (Suppurative) Flexor Tenosynovitis: Assessment and Management (Eplasty, 2016); Paronychia: MedlinePlus Medical Encyclopedia (MedlinePlus (U.S. National Library of Medicine), 2024).

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Representative model, for educational purposes only.

Flexor tendon sheaths highlighted on the Durgical 3D model