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What is the difference between erythema and cellulitis?

Published in Dermatology 2 mins read

Erythema is a redness of the skin, while cellulitis is a bacterial infection causing inflammation of the skin and underlying tissues, often characterized by erythema. Erythema is a symptom, whereas cellulitis is a specific condition causing that symptom.

To further clarify, here's a breakdown:

Erythema

  • Definition: Simply put, erythema is redness of the skin caused by increased blood flow to the surface. It is a sign or symptom, not a disease itself.
  • Causes: Erythema can result from various factors, including:
    • Inflammation
    • Infection
    • Allergic reactions
    • Sunburn
    • Certain medications
  • Appearance: Reddened skin. The appearance can vary from mild pinkness to deep red.

Cellulitis

  • Definition: A bacterial skin infection affecting the deeper layers of the skin and subcutaneous tissues.
  • Causes: Usually caused by bacteria, most commonly Staphylococcus and Streptococcus. Bacteria enter through breaks in the skin (cuts, insect bites, surgical wounds, etc.).
  • Appearance: While erythema (redness) is a key feature, cellulitis also presents with:
    • Pain
    • Swelling
    • Warmth to the touch
    • Sometimes blisters or skin dimpling
    • Less well-defined borders than other conditions like erysipelas
  • Complications: Can become serious if left untreated, potentially leading to sepsis.

Key Differences Summarized:

Feature Erythema Cellulitis
Definition Skin redness; a symptom. Bacterial infection of the skin and subcutaneous tissue; a disease.
Cause Various factors (inflammation, allergy, etc.) Bacteria (usually Staphylococcus or Streptococcus).
Symptoms Redness only. Redness, pain, swelling, warmth, possible blisters, fever.
Treatment Depends on the underlying cause. Antibiotics.

In essence, seeing erythema doesn't automatically mean someone has cellulitis. Erythema is a symptom that needs further investigation to determine the underlying cause, which could be cellulitis or something else entirely.