Cellulitis is an inflammation of the dermis and subcutaneous tissue of the skin caused by a bacterial infection, with the lesion typically spreading gradually from bottom to top. Initially, the infected area may show mild erythema, followed by significant bacterial proliferation that triggers a local inflammatory response, causing the skin to progressively swell, become warm, painful, and turn red. Unlike erysipelas, which has well-defined borders, the boundaries of cellulitis are more diffuse, making it difficult to clearly distinguish the infected area from the surrounding uninfected skin.

Symptoms of Cellulitis

Clinically, the infected region not only appears red, swollen, and warm but is often accompanied by significant tenderness upon gentle pressure. If the infection spreads, patients may also experience systemic symptoms such as fever, chills, general fatigue, headache, joint pain, and swelling of nearby lymph nodes. When complications like bacteremia or sepsis occur, the condition can rapidly worsen and become life-threatening, making early diagnosis and timely treatment critical.

Causes of Cellulitis

The primary cause of cellulitis is usually bacteria entering the dermis or subcutaneous tissue through a breach in the skin’s integrity. Common causative pathogens include *Staphylococcus aureus* and *Streptococcus pyogenes* (Group A Streptococcus). In many cases, the onset is preceded by minor abrasions, cuts, insect bites, or other small wounds in the affected area. Since these injuries are often overlooked, bacteria can rapidly multiply locally. Additionally, individuals with poor blood circulation, compromised immune systems, diabetes, or chronic venous insufficiency are considered high-risk groups for cellulitis.

Treatment and Prevention

In terms of treatment, mild cases of cellulitis can often be managed on an outpatient basis with oral antibiotics. Treatment also emphasizes local care: gently cleaning the affected area daily with warm water and a mild cleanser to remove exudate and crusts, followed by covering it with a waterproof dressing to prevent further bacterial spread and cross-infection.

In cases of more severe infection or when patients exhibit systemic symptoms (such as high fever or chills), hospitalization for intravenous antibiotic therapy is often required to achieve faster and more effective results.

In summary, cellulitis is a bacterial infection characterized by redness, swelling, warmth, and pain, with a broad and poorly defined area of involvement. Early recognition, appropriate treatment, and preventive measures targeting risk factors (such as keeping wounds clean, improving blood circulation, and managing chronic conditions) are essential to prevent severe complications and shorten the disease course. Proactive treatment typically leads to improvement in most patients within a few days, preventing the spread of infection and the development of sepsis or other complications.