A cut is likely becoming infected if the redness, swelling, or pain around it gets worse instead of better after the first two to three days, especially if you notice thick yellow or green drainage, spreading redness, red streaking, or fever. Mild redness and tenderness right after an injury is a normal part of healing. Here is how to tell the difference and when it is time to get care.

1. Normal Healing Response (Not Infected)

What it is: The expected redness, mild swelling, and tenderness that most cuts show in the first few days as the body repairs the skin.

Why it happens: Blood vessels widen and immune cells move into the area to clear debris and start rebuilding tissue, which causes mild, temporary inflammation.

Common symptoms: Slightly pink or red edges, minor warmth and swelling, and a small amount of clear or faintly pink fluid, all of which improve day by day.

Risk factors: Any cut can show this response; it is not a sign of a problem on its own.

When to seek evaluation: If redness and swelling are shrinking and less tender than the day before, no evaluation is needed. Keep the wound clean, covered, and dry.

2. Localized Superficial Infection

What it is: A bacterial infection limited to the skin right around the cut, usually starting once bacteria enter through the broken skin.

Why it happens: Common skin bacteria get into the wound, and instead of the steady improvement seen in normal healing, the immune response causes worsening inflammation.

Common symptoms: Redness that spreads or deepens after day three, swelling and warmth that increase rather than fade, growing tenderness, and sometimes cloudy or yellowish drainage.

Risk factors: Dirty or deep wounds, animal or human bites, delayed cleaning, diabetes, and a weakened immune system.

When to seek evaluation: See a doctor within a day or two if redness or pain is getting worse instead of better.

3. Pus or Abscess Formation

What it is: A pocket of thick fluid made of dead white blood cells, bacteria, and tissue that collects under the skin at the wound site.

Why it happens: As the immune system fights a bacterial infection, dead cells and fluid build up faster than the body can clear them, forming a walled-off collection.

Common symptoms: Thick yellow, green, or gray discharge, a foul odor, a soft or fluid-filled lump near the wound, and increasing local pain.

Risk factors: Deep puncture wounds, a retained splinter or debris in the wound, and delayed or incomplete wound cleaning.

When to seek evaluation: See a doctor soon. An abscess often needs to be drained by a clinician and should not be squeezed or opened at home.

4. Spreading Infection (Cellulitis)

What it is: An infection that has moved beyond the wound edges into the surrounding healthy skin and deeper tissue.

Why it happens: Bacteria spread outward from the original wound faster than the immune system can contain them, especially if the wound was not treated early.

Common symptoms: Redness expanding beyond the original wound border, increasing warmth and swelling, tenderness over a wider area, and sometimes a mild fever.

Risk factors: Diabetes, poor circulation, obesity, a weakened immune system, and wounds on the legs or feet.

When to seek evaluation: See a doctor the same day. Cellulitis usually needs oral or IV antibiotics and can worsen quickly without treatment.

5. Red Streaking (Lymphangitis)

What it is: Inflammation of the lymphatic vessels that drain fluid from the wound area toward nearby lymph nodes.

Why it happens: Bacteria travel from the infected wound into the lymphatic channels, and the body's inflammatory response follows the same path, creating a visible line under the skin.

Common symptoms: A thin red streak running from the wound toward the elbow, armpit, groin, or knee, along with swollen, tender lymph nodes and sometimes fever.

Risk factors: An untreated or worsening localized infection, and cuts on the hands, arms, feet, or legs.

When to seek evaluation: This needs prompt medical care, usually the same day, since it signals the infection is spreading through the body's drainage system.

6. Delayed or Non-Healing Wound

What it is: A cut that is not improving on the expected timeline, which can point to a low-grade or ongoing infection.

Why it happens: Poor blood flow, high blood sugar, or a persistent low-level bacterial presence can keep a wound inflamed instead of letting it close.

Common symptoms: A wound that looks the same or worse after one to two weeks, persistent drainage, an edge that will not close, and skin around it that stays discolored.

Risk factors: Diabetes, peripheral artery disease, smoking, older age, and wounds on the lower legs or feet.

When to seek evaluation: See a doctor if a cut has not visibly improved within about a week. Slow healing can hide a deeper infection.

7. Systemic Symptoms (Fever and Feeling Unwell)

What it is: Signs that an infection is affecting more than just the skin around the wound.

Why it happens: When a local infection is not controlled, bacteria or their toxins can enter the bloodstream and trigger a body-wide immune and temperature response.

Common symptoms: Fever, chills, fatigue, body aches, and a wound that keeps worsening despite home care.

Risk factors: A delayed or untreated local infection, a weakened immune system, diabetes, and chronic illness.

When to seek evaluation: See a doctor the same day. Fever with a worsening wound is not something to wait out at home.

8. Sepsis

What it is: A rare but life-threatening reaction that happens when the body's response to an infection starts injuring its own organs and tissues.

Why it happens: An infection that starts in a wound can, in uncommon cases, spread into the bloodstream and trigger this extreme, whole-body inflammatory response.

Common symptoms: A high fever or an unusually low body temperature, a fast heart rate, rapid breathing, confusion, extreme weakness, and a wound that looks severely worsened.

Risk factors: Older age, diabetes, a weakened immune system, chronic illness, and a wound infection that was left untreated.

When to seek evaluation: This is a medical emergency. Call 911 or go to the emergency room immediately.

9. Necrotizing Soft Tissue Infection

What it is: A rare, fast-moving, and severe infection that destroys skin, fat, and the tissue covering muscle.

Why it happens: Certain aggressive bacteria, sometimes called "flesh-eating bacteria" in the media, invade deep tissue and spread rapidly, cutting off blood supply as they go.

Common symptoms: Pain that feels far more intense than the wound looks like it should cause, rapidly spreading redness or discoloration, skin that may blister or turn dusky or black, swelling, and fever.

Risk factors: Deep or dirty wounds, diabetes, a weakened immune system, and recent surgery, though it can occur in otherwise healthy people too.

When to seek evaluation: This is a surgical emergency. Call 911 or go to the emergency room immediately, since this condition can become life-threatening within hours.

When to Seek Medical Care