Cellulitis: causes, symptoms, diagnosis, treatment and prevention

Causes and risk factors

The most frequent bacterial causes are Staphylococcus and Streptococcus species, which enter through breaks in the skin. Common portals include cuts, abrasions, insect bites, surgical wounds and fissures from dry skin. Underlying conditions that increase risk include chronic swelling of a limb, athlete's foot, diabetes, immune suppression and intravenous drug use.

Signs, diagnosis and when to seek care

Typical findings are localized redness that spreads, pain, warmth and swelling. Lymph nodes may be tender and a fever can develop. Diagnosis is usually clinical; blood tests, wound cultures or imaging are used when the presentation is severe, atypical or when an abscess or deeper infection is suspected. Prompt medical assessment is important for rapidly progressing disease or systemic symptoms.

Treatment

Mild cellulitis is commonly treated with oral antibiotics targeting streptococci and staphylococci, along with elevation of the limb and pain relief. More severe cases require intravenous antibiotics and sometimes hospital care. If an abscess forms, incision and drainage may be necessary. Treatment choice is guided by severity, likely organisms and local antibiotic resistance patterns.

Complications and prevention

Potential complications include recurrent episodes, spread to deeper tissues (for example, necrotizing infection rarely), and bloodstream infection. Preventive measures focus on skin care: clean and protect breaks in the skin, treat fungal infections between toes, control chronic swelling, and manage chronic diseases such as diabetes. Early treatment of small wounds reduces risk.

Distinctions and notable facts

• Cellulitis vs erysipelas: erysipelas is a more superficial, sharply demarcated infection often caused by Streptococcus.
• Cellulitis vs cellulite: the two are unrelated; cellulite is a cosmetic term for subcutaneous fat irregularity.
• Conditions that can mimic cellulitis include deep vein thrombosis, contact dermatitis, gout and insect bite reactions; clinical assessment is key.

Further resources

• Overview and definitions
• Skin anatomy and layers
• Bacterial causes
• Facial cellulitis considerations
• Cellulite vs cellulitis explanation
• Staphylococcus information
• Streptococcus information
• Wound care guidance
• Insect bite management
• Immune system and infection risk
• Fever and systemic signs