Wound Infection

Normal healing vs infection

Causes and risk factors

Bacteria from the skin, the environment or the object that caused the wound enter through the break in the skin. Risk is higher with:

• dirty wounds, soil or debris, rusty objects
• bites: cat bites are especially prone to infection; human and dog bites also carry mixed bacteria. See animal bite
• puncture wounds and crush injuries
• delays in cleaning or closing a wound
• diabetes, poor circulation, obesity, smoking
• weakened immunity, steroid use
• wounds on the feet or legs

Types of wound infection

• local infection: redness, warmth and pus confined to the wound
• cellulitis: infection spreading through the skin around the wound
• abscess: a walled-off pocket of pus
• lymphangitis: red streaks along lymph channels
• surgical site infection: infection after an operation
• necrotizing fasciitis: rare, rapidly spreading, life-threatening infection of deep tissues
• tetanus: toxin from soil bacteria causing muscle spasms; prevented by vaccination

Diagnosis

Wound infection is usually diagnosed by examination. A swab of pus may be sent for culture, particularly for severe, recurrent or non-healing infections or suspected MRSA. Blood tests and imaging (X-ray, ultrasound or MRI) help with deep infections, foreign bodies or possible bone infection.

Treatment

Home care for minor wounds

1. wash your hands
2. rinse the wound under clean running water for several minutes
3. clean around the wound with mild soap; avoid hydrogen peroxide or iodine directly in the wound, which can damage tissue
4. apply a thin layer of petroleum jelly or an antibiotic ointment
5. cover with a clean dressing and change it daily or when wet or dirty
6. watch for signs of infection

Medical treatment

• antibiotics: oral antibiotics for spreading redness or deeper infection; IV antibiotics for severe infection. Choice depends on the wound type and MRSA risk; bites usually need amoxicillin-clavulanate
• drainage: opening and draining pus pockets
• debridement: removing dead tissue or debris
• tetanus booster if your last dose was more than 5 years ago for a dirty wound, or 10 years for a clean wound
• surgery for necrotizing infections

Take the full course of antibiotics and return if not improving within 48 to 72 hours.

Prevention

• clean wounds promptly and keep them covered
• seek care for deep, gaping, dirty or bite wounds
• keep tetanus vaccinations up to date
• control blood sugar if you have diabetes
• check feet daily if you have diabetes or neuropathy
• do not pick scabs

Frequently asked questions

How do I know if my wound is infected?

Signs of infection include pain that gets worse instead of better, redness that spreads, warmth, swelling, pus or cloudy drainage, a bad smell and fever. A thin pink rim and clear fluid in the first few days are usually part of normal healing.

How do you treat an open wound infection?

Mild infections may improve with cleaning and fresh dressings, but most infected wounds need medical review. Treatment may include antibiotics, draining pus and removing debris. Seek urgent care for spreading redness, red streaks, fever or severe pain.

Can an infected wound heal on its own?

Very mild infection may settle with good wound care, but infection can spread to the skin, blood or bone. If redness spreads, pain worsens or fever develops, see a doctor rather than waiting.

When is a wound infection an emergency?

Get emergency care for rapidly spreading redness, severe pain out of proportion to the wound, skin turning dark or blistering, fever with confusion or a racing heart, or jaw stiffness and muscle spasms. These can signal necrotizing infection, sepsis or tetanus.