A 49-year-old man had a 10-year history of recurrent pruritic papules that were initially treated as atopic dermatitis. Laboratory examination showed marked eosinophilia with an absolute eosinophil count of 5.29 × 10^9/l and a total IgE above 6,000 IU/ml (norm 0–100 IU/ml). After initiation of upadacitinib for refractory pruritus, pruritus decreased, revealing distal numbness and gait instability. Nerve conduction studies showed symmetric sensory polyneuropathy with axonal disruption and skin biopsy showed eosinophilic infiltration without vasculitis. The density of intraepidermal nerve fibers was normal for age. After excluding other causes, the diagnosis of idiopathic hypereosinophilic syndrome with involvement of the skin and peripheral nerves was made. Treatment with mepolizumab (300 mg subcutaneously every 4 weeks) resulted in improvement of neuropathic symptoms and a decrease in eosinophils. The case highlights the need for electrophysiological examination in chronic pruritus with eosinophilia.