Prurigo of hebra is most probably caused by which of the following?

Prurigo of hebra is a chronic, recurrent skin disorder characterised by intensely pruritic papules and nodules in the trunk and limbs. It usually begins during infancy in the form of an uicarial rash followed by millet-sized or slightly larger pruritic papules that eventually become covered by a blood-coloured crust. Itching of various intensities are observed. Both sexes affected, onset between 1 and 5 years of age. Most cases occurred in atopic subjects and the role of poor nutritional and hygienic conditions were considered as predisposing factors. The possibility that some cases represent papular uicaria modified in an atopic subject must be considered. The treatment is that of atopic dermatitis.