An infected wound or skin area typically shows five key signs: redness, swelling, warmth, pain, and discharge. These can range from subtle pink discoloration around a small cut to dramatic color changes, streaking, and pus that signal something more serious. Knowing exactly what to look for helps you catch an infection early, before it has a chance to spread.
The Five Classic Signs of Infection
Redness is usually the first thing you notice. The skin around a wound or affected area turns pink, red, or purple depending on your skin tone. On darker skin, the color change may appear as a deepening of your natural tone rather than obvious redness, making it easier to miss. The discolored area often feels warm or hot to the touch compared to surrounding skin.
Swelling follows closely behind. The tissue around the site puffs up as your immune system sends fluid and white blood cells to fight off invading bacteria. Mild swelling in the first few days after an injury is a normal part of healing, but swelling that gets worse after three or four days, or that expands beyond the immediate wound area, points toward infection.
Pain that increases rather than decreases over time is another red flag. A healing wound gradually hurts less. An infected one does the opposite: it throbs, aches, or becomes tender to the touch even days after the initial injury. If you bump the area lightly and the pain seems out of proportion, that’s worth paying attention to.
What Infected Discharge Looks Like
Not all wound drainage means trouble. In the first few days of healing, clear to slightly yellow fluid (called serous drainage) is completely normal. You might also see pinkish fluid, which is just that clear drainage mixed with a small amount of blood. Neither of these indicates infection.
The discharge that signals infection is purulent drainage, commonly known as pus. It’s thicker than normal wound fluid and appears milky white, yellow, green, or brown. It almost always smells bad. If you notice the color or odor of discharge changing over time, that typically means the infection is worsening. Green or yellow-green pus is especially distinctive and hard to miss.
Skin Infections vs. Fungal Infections
The shape and pattern of redness tells you a lot about what kind of infection you’re dealing with. Bacterial skin infections like cellulitis create a spreading patch of red, warm skin without a clear border. The redness fades gradually into normal skin at the edges, and the whole area feels swollen and tender.
Fungal infections look quite different. Ringworm, for example, creates a nearly circular lesion with a reddish, scaly outer ring and skin that looks relatively normal in the center. That ring shape with central clearing is the hallmark of a fungal infection and won’t appear in bacterial infections. Fungal patches also tend to itch more than they hurt, while bacterial infections lean toward pain and tenderness.
Another bacterial pattern to know: erysipelas, a type of skin infection that creates a raised, bright red area with a sharply defined border. Unlike cellulitis’s fuzzy edges, erysipelas looks almost like someone drew a line where the infection stops. Both need treatment, but the visual difference helps identify what you’re dealing with.
Red Streaks and Spreading Redness
Red streaks extending outward from a wound are one of the most urgent visual signs of infection. These streaks indicate that infection has entered your lymphatic system, a condition called lymphangitis. The streaks follow the path of lymph vessels under your skin, often running from the wound toward the nearest lymph nodes (in your armpit or groin, for example).
This type of infection moves fast. Within less than 24 hours, it can spread from the original wound to multiple areas of your lymphatic system. Left unchecked, the bacteria can enter your bloodstream and cause sepsis. If you see red streaks radiating from any wound, that warrants same-day medical attention.
What an Infected Throat Looks Like
Infection isn’t limited to skin and wounds. If you’re checking your throat with a flashlight and mirror, here’s what to look for: bright red, swollen tonsils with white spots or patches are a strong visual indicator of strep throat. Those white patches are collections of pus on the tonsil surface and distinguish bacterial infection from a viral sore throat, which typically causes redness and swelling without those white spots.
Infected Wounds After Surgery
Surgical site infections have their own timeline and appearance. Most show up within the first 30 days after surgery. In the first zero to four days, some redness and swelling around an incision is part of the normal healing process as your immune cells clean up debris at the wound site.
What’s not normal: wound edges that are red or dusky rather than pink, increasing redness that spreads beyond the incision line, or edges that pull apart rather than staying together. Healthy healing wounds have pink edges that gradually close. Infected ones may have rolled or raised edges with discolored skin, and you may notice thick discharge soaking through your bandage. Any pus or foul smell from a surgical incision needs prompt evaluation.
When Infection Becomes Systemic
Sometimes infection moves beyond its original site and affects your whole body. The visual and physical signs shift from local to systemic at that point. A fever above 100.4°F (or a drop below 96.8°F), a heart rate above 90 beats per minute, and fast, shallow breathing above 20 breaths per minute are the vital sign thresholds that signal your body is mounting a system-wide response to infection.
More advanced systemic infection, or sepsis, produces symptoms you can observe without any medical equipment: confusion or a sudden change in mental clarity, sweating for no obvious reason, shivering, lightheadedness, and skin that looks mottled or unusually pale. Septic shock takes this further, with extreme drowsiness, inability to stand, and profound confusion. Fast breathing combined with confusion is the combination that needs emergency care immediately.
Tracking Changes Over Time
One of the most practical things you can do with a wound you’re watching is track its appearance. Take a photo each day with your phone, ideally in the same lighting. Some people draw a line around the border of redness with a pen so they can tell at a glance whether it’s expanding. If the redness spreads past your pen mark within hours, that’s a clear sign the infection is progressing.
The overall pattern matters more than any single sign. A wound that’s slightly pink and a little swollen on day two is probably healing normally. A wound that’s redder, more swollen, more painful, and producing thicker discharge on day five than it was on day three is telling you something has changed. Infection generally follows a trajectory of worsening, not fluctuation. Things that are getting better don’t suddenly reverse course without a reason.