Cellulitis appears as an expanding patch of pink or red skin that feels warm, swollen, and tender to the touch. Unlike a rash with clear edges, the redness in cellulitis fades gradually into the surrounding skin, making it hard to tell exactly where the infection ends. It most commonly shows up on one lower leg, though it can develop anywhere on the body.
The Four Hallmarks of Cellulitis
The classic signs are redness, swelling, warmth, and pain. These four features together point strongly toward cellulitis, and they develop because the infection sits deep in the skin and the fat layer beneath it. The redness tends to be more of a pinkish tone than a vivid, bright red. The skin often looks flat rather than raised, and the swollen area may feel tight or stretched.
As the infection progresses, you might also notice skin dimpling, where the surface takes on an orange-peel texture. In more advanced cases, blisters or fluid-filled sacs can form over the affected area. Spots or small red dots sometimes appear within the patch of redness. The area is typically painful even without pressing on it, and pressing makes the tenderness significantly worse.
How the Borders Look
One of the most distinctive visual features of cellulitis is its blurry, poorly defined border. The redness doesn’t have a sharp line separating it from healthy skin. Instead, it gradually blends outward. This is actually a useful clue: a related but more superficial infection called erysipelas produces bright red, raised skin with clearly defined edges. Cellulitis, by contrast, looks flatter, pinker, and fuzzier at the margins.
Because the borders are indistinct, doctors often use a pen or marker to outline the edge of the redness on your skin. This creates a visible reference point so you can tell whether the infection is spreading over the next 24 to 48 hours. If you’re monitoring at home, this is something you can do yourself with a simple marker.
Where It Usually Appears
Cellulitis overwhelmingly affects just one side of the body. If both of your lower legs are red and swollen, that pattern strongly suggests something other than cellulitis. The lower legs are the most common site, but cellulitis can also develop on the arms, face, or any area where bacteria have entered through a break in the skin, whether from a cut, insect bite, surgical wound, or cracked dry skin.
Red Streaks Spreading From the Area
Sometimes red, irregular, warm streaks develop on the skin and extend from the infected area toward nearby lymph nodes, such as in the groin or armpit. This is a sign that the infection has reached the lymph vessels. These streaks are tender to touch and look like thin red lines running along the surface of the skin. Their appearance signals that the infection is moving beyond the original site and needs prompt treatment.
How Cellulitis Differs From Stasis Dermatitis
Stasis dermatitis is the most commonly confused condition. It happens when poor circulation causes fluid to pool in the lower legs, producing redness, swelling, and sometimes weeping or flaking skin. The key differences are visual and practical. Stasis dermatitis is almost always bilateral, affecting both legs. It develops slowly over months or years, and the skin often shows dark brownish pigmentation from long-standing fluid buildup. The legs are generally not tender to touch.
Cellulitis, on the other hand, is one-sided, comes on within days, and hurts. If you’ve had gradually worsening redness in both legs for a long time, that’s a very different picture from sudden, painful swelling appearing in one leg over a few days. Patches of skin that look darkened, thickened, or “bound down” to the tissue underneath also point toward a chronic condition rather than an acute infection.
Signs the Infection Is Getting Worse
After the initial redness and swelling appear, there are specific visual and physical changes that signal the infection is progressing. The redness expands beyond any line you’ve drawn on the skin. Large blisters develop over the affected area. Fever becomes persistent. The pain intensifies rather than staying stable or improving. Any of these changes mean the infection is not being controlled and needs reassessment.
Cellulitis is diagnosed entirely by how it looks and feels. There’s no blood test or imaging study that confirms it. That makes recognizing the visual pattern especially important: one-sided, warm, tender, pink-to-red skin with blurred borders that spreads over hours to days.