Signs of Wound Infection After Surgery (When to Call vs Go to the ER)

Surgical site infections (SSIs) affect roughly 2-5% of surgical wounds in the U.S. They’re one of the most preventable post-op complications, and most are caught early when patients (or caregivers) know what to look for. Knowing the difference between normal healing and infection — and the difference between an infection that needs a phone call versus an ER trip — is one of the most useful skills you can develop in the weeks after surgery.

This guide draws on wound-care nursing standards and Johns Hopkins Patient Education materials. It’s not a substitute for the discharge instructions from your specific surgeon, but it’s the framework for what those instructions are actually telling you.

What normal post-op healing looks like

The first 3-7 days after surgery, expect:

• Mild swelling around the incision. Generally diminishes day-by-day.
• Some pink or red coloration along the incision line, extending no more than 1-2 cm beyond.
• Small amount of clear or slightly blood-tinged drainage for the first 24-48 hours.
• Tenderness at the incision, gradually improving.
• Bruising spreading from the site — can be impressive in color, normal in appearance.
• Itching as healing progresses, typically starting after the first week.

By day 7-14:

• Incision should appear closed and dry
• Redness should be fading
• Bruising clearing
• Tenderness mostly resolved
• No drainage

By 4-6 weeks:

• Incision well-healed, possibly slightly raised or pink scar
• Sensation returning to surrounding skin
• Some occasional itching or twinges as nerves regenerate

If your wound looks dramatically different from this trajectory at any point, that’s the trigger for evaluation.

Signs of infection: the classic five

Wound-care nurses teach a five-sign rubric. Any combination of three or more warrants medical evaluation:

1. Increasing redness spreading beyond the incision line. Not just present — worsening compared to yesterday. A faint pink rim is normal; bright red expansion is not.
2. Increasing pain at the wound after the first 3-4 days. Post-op pain should follow a downward trajectory; pain that’s worse on day 5 than on day 2 is concerning.
3. Increasing swelling after the first 48-72 hours.
4. Warmth — the skin around the incision is noticeably warmer than the surrounding skin.
5. Drainage that’s thick, opaque, yellow, green, brown, or foul-smelling. Clear or pink-tinged is normal for the first day or two. Cloudy yellow/green pus is not.

The mnemonic in nursing school is “hot, red, swollen, painful, draining.”

Systemic signs of infection

The wound is the local sign. Systemic signs mean the infection has gotten into your bloodstream or is generating a body-wide inflammatory response:

• Fever over 101°F (38.3°C). A low-grade fever (under 100.4) in the first 1-2 days is common from the inflammatory response to surgery itself. After day 3, any fever is suspicious. Above 101 is a same-day call.
• Chills or shaking.
• Increased fatigue beyond what you’d expect for normal recovery.
• Nausea or vomiting not related to medications.
• Increased heart rate at rest.

The decision tree: call vs ER

Call your surgeon’s office (same day or after-hours line)

• Two or three of the local signs (mild redness expansion, increasing tenderness, mild warmth)
• Fever 100.4-101
• Small amount of cloudy drainage
• Wound looks “different” from yesterday but you’re not sure if it’s healing weird vs infected
• Pain that’s not responding to prescribed medication but isn’t severe

Go to urgent care or ER

• Fever over 101
• Significant pus drainage or foul odor
• Red streaks extending from the wound (possible spreading infection through lymphatics)
• Wound edges separating (dehiscence)
• Severe, increasing pain
• Any concerning combination of systemic symptoms (fever + chills + heart racing)

Call 911

• High fever with confusion or difficulty staying alert
• Difficulty breathing
• Wound bleeding heavily and not stopping with direct pressure
• Signs of sepsis: fever or low temp + rapid heart rate + rapid breathing + confusion
• Wound opening with internal contents visible

How to assess the wound properly

Daily visual check is the standard. Make it the same time each day — before showering is convenient because you’ll have good lighting in the bathroom.

1. Wash your hands thoroughly with soap and water.
2. Carefully remove any dressing per your surgeon’s instructions.
3. In good light, examine the entire length of the incision.
4. Compare to yesterday — better, same, or worse?
5. Note any drainage on the old dressing.
6. Take a phone photo if anything looks different — useful both for tracking and for sending to the surgeon’s office.
7. Redress per instructions (don’t replace a dressing the surgeon told you to leave off).

Wound care basics

• Keep the wound clean and dry per surgeon’s instructions. Modern guidance often allows showering after 24-48 hours; baths and swimming are typically restricted longer (until full closure, often 2-4 weeks).
• Don’t apply ointments, creams, or hydrogen peroxide unless specifically prescribed. Hydrogen peroxide damages healing tissue. Antibiotic ointments are often unnecessary on a clean surgical wound and can cause skin reactions.
• Pat dry, don’t rub. Use a clean towel.
• Change dressings as instructed — usually daily or when wet. Always with clean hands.
• Don’t pick at scabs, stitches, or staples. Sutures and staples are removed at the follow-up appointment; absorbable sutures dissolve on their own.
• Don’t expose to direct sun for 6-12 months — UV exposure on a healing scar causes permanent darkening.

Special situations

Joint replacement wounds

Larger surface area, longer healing time, higher infection consequence. Prosthetic joint infections require surgery to clean out and sometimes prosthesis replacement — this is the worst-case scenario your surgeon is screening for at every follow-up. Take wound symptoms more seriously, not less, after joint replacement.

Abdominal wounds

Risk of dehiscence (wound coming apart) with coughing, sneezing, lifting, or straining. Hold a pillow firmly against the incision when coughing/sneezing for the first 2-3 weeks. Sudden severe pain at the wound with a popping sensation is dehiscence until proven otherwise — ER trip.

Diabetic patients

Significantly higher infection risk, slower healing, more subtle infection signs (fever response can be blunted). Check the wound twice daily. Tight blood sugar control during recovery is critical for healing.

Immunocompromised patients (chemotherapy, immunosuppressants)

Infection can present with minimal local signs and rapid systemic deterioration. Have a much lower threshold for calling the surgical team about any wound concerns.

What to have at home

• Surgeon-prescribed dressings in adequate supply for the planned dressing changes
• Saline solution or sterile water for wound cleansing (if your surgeon recommends)
• Surgical tape (paper tape is gentlest on skin)
• Sterile gauze pads
• Disposable gloves for caregivers handling the wound
• Thermometer (digital, oral or temporal artery)
• Phone numbers: surgeon’s office daytime line, after-hours line, primary care, pharmacy

FAQ

I’m on antibiotics from surgery — doesn’t that prevent infection?

Prophylactic antibiotics reduce infection risk but don’t eliminate it. Some bacteria are resistant; some infections develop after the prophylactic course ends. Continue monitoring the wound throughout the healing period regardless of antibiotic prescriptions.

The wound has a small amount of clear fluid coming out for the 4th day in a row. Is that okay?

Persistent drainage past 48-72 hours is worth a call to the surgeon’s office. It may be normal serous fluid (clear/pink, no odor, decreasing) or it may be early infection or a developing seroma. Photo + phone call is the right move.

My wound itches like crazy. Is that infection?

Usually no — itching is a normal healing sign as nerves regenerate. Suspicious for infection only if combined with the other signs (redness, warmth, drainage). Itching alone, with the wound otherwise looking good, is reassuring.

Should I check my temperature regularly?

Twice daily for the first week is reasonable, then daily through week 2. Track the trend — a steady low-grade fever isn’t the same as a normal day followed by 102 the next.

I had surgery on the weekend and my surgeon doesn’t pick up. What do I do?

Most surgical practices have an after-hours line that routes to either the on-call surgeon or to the hospital’s nursing service for surgical patients. The discharge papers list the number. If you can’t reach anyone and you have any of the urgent-call signs above, go to urgent care or the ER — better to be evaluated and sent home than to wait. For the equipment side of recovery, see what to have at home before knee replacement surgery.