One cousing said he had something called well's syndrome (eosinophilic cellulitis?). what causes it?

Wells Syndrome: Wells syndrome (eosinophilic cellulitis) is an uncommon condition of unknown etiology. The presentation usually involves a mildly pruritic or tender cellulitis-like eruption with typical histologic features characterized by edema, flame figures, and a marked infiltrate of eosinophils in the dermis.Papular and nodular eruptions at the clinical presentation have also been reported.