In short. A surgical site infection announces itself by going the wrong way after the first few days: redness spreading outward, skin hot to touch, pain increasing instead of easing, swelling that grows after it had begun to settle, thick or foul-smelling discharge, or fever. Superficial infection often responds to tablets; deeper infection or systemic illness needs hospital assessment.
Key points
- Normal healing peaks early and improves; infection appears or worsens after day three or four.
- Spreading redness, heat, increasing pain, pus, or fever are the signals.
- Tablets may not reach a collection of fluid or a deeper plane.
- Worsening on treatment is itself a reason for examination, not another prescription.
- Fever with chills, confusion, or feeling very unwell is an emergency.
How is infection different from ordinary healing?
In the first days a wound is expected to be tender, slightly swollen, and a little pink at its edges. A small amount of clear or blood-stained fluid is normal, as is mild bruising. Some procedures produce a low-grade temperature in the first day or two. Normal inflammation is at its worst early and then improves steadily. Infection behaves differently: it appears or worsens after the first few days, and it keeps going in the wrong direction.
| Normal healing | Infection | |
|---|---|---|
| Timing | Worst in first 2–3 days, then improves | Appears or worsens after day 3–4 |
| Redness | At the wound edge, fading | Spreading outward |
| Temperature | Warm, settling | Hot compared with the other side |
| Pain | Easing | Increasing, throbbing, worse at night |
| Discharge | Clear or blood-stained | Thick, yellow or green, offensive |
| Fever | Low-grade, first day or two | Fever, chills, shivering |
What are the signs to watch for?
Redness that spreads outwards from the wound. Skin that feels hot compared with the other side. Pain that increases instead of easing, particularly throbbing pain or pain worse at night. Swelling that increases after it had begun to settle. Discharge that becomes thick, yellow, or green, or smells unpleasant. A wound that separates. Fever, chills, shivering, or a general feeling of being unwell.
Why are tablets sometimes not enough?
An antibiotic tablet has to reach the infected tissue through the bloodstream. If the infection sits in a collection of fluid, behind a wall of inflamed tissue, or in a deeper plane than the medicine penetrates well, tablets may not control it. That is why worsening signs while on treatment are themselves an important signal, and why an examination matters more than a repeat prescription.
Are injectables different?
Infection after an injectable usually appears as redness, warmth, and tenderness days to weeks afterwards, sometimes with a small collection of pus. It can also appear late, months after treatment. Any nodule or area that becomes painful, red, or fluctuant should be examined. Do not attempt to drain it yourself, and do not assume a late reaction is harmless.
When is it an emergency?
- Contact the treating team the same day if redness is spreading, the area is hot and increasingly painful, or there is pus or foul-smelling discharge.
- Seek urgent care if there is fever with chills or shivering, a rapid heart rate, confusion, or you feel very unwell.
- Do not squeeze, drain, or apply heat, and do not start or stop antibiotics without advice.
Sources
- NICE — guidance on surgical site infection
- World Health Organization — surgical safety guidance
- CDC — surgical site infection resources
Internal links
Frequently asked questions
How can I tell an infection from ordinary healing?
Normal inflammation is at its worst early, then improves steadily. Infection appears or worsens after the first few days and keeps going in the wrong direction: redness spreading outwards, skin hot to touch, pain increasing rather than easing, swelling that grows after it had begun to settle, or thick, yellow or foul-smelling discharge.
When does an infection stop being a call and become an emergency?
Contact your treating team the same day if redness is spreading, if the area is hot and increasingly painful, or if there is pus or foul-smelling discharge. Seek urgent care at the nearest emergency department if you have fever with chills or shivering, a rapid heart rate, confusion, or you feel generally very unwell.
Can an infection appear months after an injectable?
Yes. After an injectable, infection usually appears as redness, warmth and tenderness days to weeks afterwards, sometimes with a small collection of pus, but it can also appear late, months after treatment. Any nodule or area that becomes painful, red or fluctuant should be examined. Do not attempt to drain it yourself.
Risks & Limitations
- Most recoveries are uneventful, but a minority of complications are time-critical and are measured in hours rather than days.
- Delay is the main factor that turns a treatable problem into a permanent one, which is why this guide asks you to make contact early rather than to wait and see.
- This guide cannot replace an in-person assessment. It describes general warning signs, not your own case, and it cannot tell you what is happening in your tissue.
- Your own treating team's aftercare instructions take precedence over anything written here. If they differ from this guide, follow your team.
- Some complications described here are rare. Reading about them is not a reason to expect them, and it is not a substitute for asking your team what specifically to watch for.
When to Seek Care
- Difficulty breathing, chest pain, or a swollen and painful calf — call emergency services or attend the nearest emergency department immediately.
- Sudden change or loss of vision — attend the nearest emergency department immediately, and say what procedure you had.
- Severe pain out of proportion to the procedure, or skin turning white, grey, mottled or dusky after an injectable.
- Uncontrolled bleeding, or a flap or graft turning dark or cold.
- Fever, spreading redness, pus or foul-smelling discharge from a wound, or a wound that is opening — contact your treating team the same day, or the hospital main line if the team cannot be reached.
References & Further Reading
- World Health Organization (WHO) — patient safety and emergency care resources
- National Institute for Health and Care Excellence (NICE, UK) — relevant clinical guidance
- American Society of Plastic Surgeons (ASPS) — procedure and safety guidance
- Resuscitation Council — basic life support and emergency response guidance
This page is patient education, not medical advice, and it does not cite individual studies. It cannot diagnose your situation and it does not replace an examination. In an emergency, call emergency services or attend the nearest emergency department. To contact the team at Chongqing West District Hospital, see Contact & Emergency Guidance.