Cellulitis causes an area of skin to become red, swollen, warm, and painful. It’s a bacterial infection of the deeper layers of skin and the tissue just beneath it, and it can spread quickly if untreated. The symptoms usually appear on one side of the body, most often on a leg, and they tend to worsen over hours to days.
How Cellulitis Looks and Feels
The earliest sign is often a patch of skin that looks slightly discolored and feels warm to the touch. Within hours, that patch typically expands into a more obvious area of redness with swelling and tenderness. The skin may feel tight or stretched because of the swelling underneath.
As the infection progresses, you may notice:
- Spreading redness that grows outward from the initial site, sometimes with poorly defined borders
- Swelling that makes the skin look puffy or glossy
- Warmth that’s easy to feel when you place your hand over the area
- Pain or tenderness even with light pressure
- Spots or dimpling on the skin surface, giving it a texture sometimes compared to an orange peel
- Blisters that may form on the surface of the affected skin
The affected area is almost always on one side of the body. This is one of the simplest ways to distinguish cellulitis from conditions like chronic vein problems in the legs, which typically cause similar-looking skin changes on both sides and don’t come with significant tenderness or fever.
Whole-Body Symptoms
Cellulitis isn’t just a skin problem. When the infection triggers a stronger immune response, you can develop fever, chills, and a general feeling of being unwell. These systemic symptoms suggest the infection is more than superficial and may be spreading into deeper tissue or the bloodstream.
Not everyone with cellulitis gets a fever. Mild cases may stay limited to local skin changes. But when fever and chills do appear, they signal that the body is fighting harder to contain the infection, and that’s the point where treatment becomes more urgent.
Red Streaks Near the Infection
Sometimes you’ll notice red streaks extending outward from the infected area, often following a line toward the nearest lymph nodes (in the groin for a leg infection, or in the armpit for an arm infection). These streaks indicate that the infection has spread into the lymphatic channels just under the skin, a condition called lymphangitis. It’s a clear visual signal that the bacteria are on the move and that the infection needs prompt treatment.
Where Cellulitis Usually Appears
The lower legs are the most common site, partly because they’re prone to small cuts, insect bites, and cracks in dry skin that give bacteria a way in. Swelling from poor circulation or conditions like athlete’s foot also makes the lower legs more vulnerable. But cellulitis can develop anywhere on the body, including the face, arms, hands, and feet.
On the face, cellulitis tends to cause dramatic swelling around the eyes or cheeks. On the legs, the swelling can be harder to distinguish from other causes of leg puffiness, which is why the combination of one-sided redness, warmth, and tenderness is the key pattern to recognize.
How Quickly Symptoms Change
Cellulitis can progress from a small warm patch to a large, painful area of swelling in a matter of hours. The speed varies depending on the type of bacteria involved and how well your immune system responds, but the general trend is that untreated cellulitis gets noticeably worse each day. Some people wake up with mild redness and by evening see that the area has doubled in size.
One practical tip: if you’re watching a suspicious area, use a pen to draw a line around the border of the redness. Check it a few hours later. If the redness has clearly expanded past your mark, that’s a reliable sign the infection is spreading and needs medical attention quickly.
Warning Signs of a Dangerous Infection
Most cellulitis responds well to antibiotics, but in rare cases, what looks like cellulitis is actually a deeper, more dangerous infection called necrotizing fasciitis. Research comparing the two conditions identified several red flags that significantly increase the likelihood of this more serious diagnosis:
- Pain out of proportion to how the skin looks. The area hurts far more than the visible redness would suggest.
- Blood-filled blisters (hemorrhagic bullae) on the skin surface
- Skin that turns dark, gray, or black, indicating tissue death
- Low blood pressure, dizziness, or feeling faint
- Confusion or altered mental state
- Redness that keeps spreading past its margins despite treatment
No single one of these findings is enough to confirm the diagnosis on its own, but a study in the International Journal of Infectious Diseases found that the presence of three or more of these signs together made necrotizing fasciitis very likely. Conversely, when all nine red flags were absent, the more dangerous infection was essentially ruled out.
What Happens if Cellulitis Goes Untreated
Left alone, cellulitis can lead to serious complications. Bacteria from the skin can enter the bloodstream, causing a body-wide infection. In severe cases, untreated cellulitis can progress to bone infections, toxic shock syndrome, or sepsis. These outcomes are uncommon with timely antibiotic treatment, but they illustrate why cellulitis isn’t something to wait out.
Recurrence is also common. People who’ve had cellulitis once are more likely to get it again, particularly if the underlying risk factors (skin breaks, swelling, weakened immune function) haven’t been addressed. Repeated episodes can damage the lymphatic system in the affected area, leading to chronic swelling that in turn makes future infections even more likely.