Cellulitis vs Erysipelas: How to Tell Them Apart and How They Are Treated

Cellulitis and Erysipelas are bacterial skin infections that affect different depths of the skin. Both cause red, swollen, warm, tender skin together with fever. If treatment is delayed, the infection may spread to Necrotizing Fasciitis, which can be life-threatening.

Erysipelas vs Cellulitis: how to tell them apart

Erysipelas: infection of the Upper Dermis and Lymphatic vessels. The border is clearly defined and raised above the skin (Sharp Demarcation), the colour is bright red, and it usually occurs on the face or legs. Group A Streptococcus is the main cause. Cellulitis: infection of the Lower Dermis and Subcutaneous tissue. The border is not clear (Indistinct Border) and the swelling is deeper. The causes are Staph aureus, including MRSA, and Streptococcus. Both can cause high fever. Lymphangitis (inflammation of the lymph vessels) is a sign of Systemic Toxicity.

Diagnosis

Diagnosis is based on clinical features. CBC, CRP and ESR are checked if there is high fever or Systemic Toxicity. Hemoculture is taken before antibiotics are given (positive in 5% or fewer). Wound culture is taken if there is an open wound. Ultrasound is used if an Abscess is suspected. MRI is used if Necrotizing Fasciitis is suspected (Gas, Fascial enhancement).

Antibiotics: depends on severity

Mild (no fever, no risk factors): oral Cephalexin 500 mg every 6 hours or Dicloxacillin for 7-10 days. If MRSA is suspected, use Doxycycline, Clindamycin or TMP-SMX. Clear-cut Erysipelas: Penicillin V or Amoxicillin. Severe (fever, Systemic Toxicity, Lymphangitis): admission for IV Ceftriaxone, Cefazolin or Clindamycin (plus Vancomycin if MRSA is suspected), together with leg elevation. Treat the underlying source, especially Tinea pedis between the toes, which is a common entry point for the bacteria.

Frequently asked questions

Q: Do I need to be admitted? A: Yes if there is high fever, Hypotension, skin peeling, or a weakened immune system (diabetes, thyroid conditions). Q: How can I tell if it is Necrotizing Fasciitis? A: Pain that is severe and out of proportion to the skin findings, blisters, Gas; consult a surgeon promptly. Q: Can it come back? A: Yes, in about 30% of people with risk factors (Lymphedema). Q: How can I prevent it from coming back? A: Treat Tinea pedis, keep the feet dry, and use Compression if there is Lymphedema.

📞 Consult about Cellulitis/Erysipelas at Siam Dermatology — LINE @siamderm | Phone +66 61 448 7000

Written by Dr. Patara Voravutinon, Dermatologist · Last reviewed 16 July 2026