Wells syndrome (WS), also called eosinophilic cellulitis is a rare inflammatory skin disease with about 200 cases reports in the literature. It is part of eosinophilic dermatoses and presents a diagnostic challenge. We report a case of WS presenting as bacterial cellulitis. A 59 year-old woman was referred to our department with a 10-day history of a rapidly extending erysipelatoid rash of the left upper limb, non-responding to oral antibiotics. Upon physical examination, erythema with swelling and blisters were found on the left upper limb with urticarial-like lesions on the breast, the belly and on the inner thighs. The patient was admitted with presumed bacterial cellulitis and was treated with intravenous ampicillin. Blood count showed raised eosinophils (2050/ul) along with a biological inflammatory syndrome. Biopsies were performed on both bullous and urticarial-like lesions showing perivascular and interstitial inflammatory infiltrate, made essentially of eosinophils with flame figures. The diagnosis of WS was made and the patient received local and oral corticosteroids (0,5mg/kg/d) with good evolution. The rarity and clinical manifestations of WS makes it sometimes difficult to differentiate between a WS and a bacterial cellulitis. However, biological and histological findings can help the clinician make the differential diagnosis between these two diseases for a better management.