Lifestyle

Red, Warm Skin on One Leg That Keeps Spreading Can Be Cellulitis. When to Get Care

By Mike Harper · October 28, 2026

A patch of red, sore skin on the lower leg can look like a bruise, a bug bite or a rash that will fade on its own. When it feels warm, swells and keeps getting bigger, it may be cellulitis, a bacterial skin infection that health officials say should be treated early.

The Centers for Disease Control and Prevention describes cellulitis as a common bacterial infection of the deeper layers of the skin. Mayo Clinic says it is a spreading skin infection, most commonly of the lower leg, caused by bacteria entering through a break in the skin. The condition often clears up with antibiotics, but Mayo Clinic warns it can spread rapidly through the body if it is not found and treated early.

These are the signs listed by the CDC, Mayo Clinic, MedlinePlus and the American Academy of Dermatology.

Red, swollen skin that feels warm. The academy says the first sign is usually red and swollen skin that often feels warm and tender to the touch. The CDC lists skin that is painful, red, swollen, tender and warm.

Redness that grows. MedlinePlus, from the National Library of Medicine, lists skin redness or inflammation that gets bigger as the infection spreads, and a sore or rash that starts suddenly and grows quickly in the first 24 hours.

One leg, not both. Mayo Clinic says cellulitis often involves the lower leg and usually just one side of the body, and the CDC says it is most common on the feet and legs. The dermatology academy notes that redness and swelling in both legs usually points to another condition.

Skin that looks tight, pitted or blistered. MedlinePlus describes a tight, glossy, stretched appearance. The CDC says the skin may look pitted, like the peel of an orange, and blisters may appear. Mayo Clinic lists spots on the skin, blisters and skin dimpling.

Fever, chills and feeling unwell. Fever and chills appear on the CDC and Mayo Clinic lists. MedlinePlus adds sweating, fatigue, muscle aches, and nausea and vomiting.

Bacteria usually get in through a crack or break in the skin, Mayo Clinic says, such as a cut, a sore, a recent surgical site, or skin affected by athlete’s foot or dermatitis. Risk factors listed by Mayo Clinic and the CDC include diabetes and other conditions that weaken the immune system, long-term swelling of the arms or legs, being overweight, shingles, and a past bout of cellulitis. Cellulitis usually does not spread from person to person.

Timing matters. Mayo Clinic advises emergency care for a swollen rash or a rash that is changing rapidly, or if you have a fever. If the rash is swollen or growing but there is no fever, it says to see a health care professional within 24 hours. The CDC says to seek medical attention immediately if the red area spreads quickly or you develop a fever or chills. Untreated cellulitis can lead to serious problems, including bloodstream and bone infections, according to the CDC and Mayo Clinic.

Doctors usually diagnose cellulitis by looking at the skin and treat most cases with antibiotics taken by mouth, the CDC says. The academy says people should notice improvement within 24 to 48 hours of starting treatment and should call the doctor’s office if they do not. Keeping the affected arm or leg raised can help reduce swelling, according to the CDC. For prevention, Mayo Clinic suggests washing wounds daily, keeping them covered, and, for people with diabetes or poor circulation, checking the feet daily and moisturizing skin to keep it from cracking.

This article is for general information and is not medical advice. Talk with your doctor about any skin changes, and seek prompt care for spreading redness, fever or chills. This article was produced with the assistance of AI and fact-checked against the sources cited by LightWave Reports.