Risk factors for recurrence of scabies: a retrospective study of scabies patients in a long-term care hospital.

A considerable number of patients suffer recurrence of scabies. To elucidate risk factors for recurrence of scabies, we compared patients who experienced scabies recurrence and those who suffered scabies only once. We conducted a retrospective review of medical records of all scabies patients in a long-term care hospital for the elderly (300 beds; six wards) for a period of 42 months to determine frequency of scabies onsets, underlying diseases, history of treatment, and demographic data such as age and sex. One hundred and forty-eight patients and five hospital staff members suffered scabies during the 42-month study period. All staff members and 98 patients had no recurrence, while 50 patients experienced at least one recurrence of scabies. The cumulative number of scabies diagnoses was 228. The rates of scabies onset and recurrence were considerably different among wards. The dementia unit showed the highest rate of onset and recurrence. In addition to frequent exposure to infectious sources, problematic behavior, such as lying in other patients beds, might cause the high recurrence rate in dementia units. Higher serum total lymphocyte count and topical use of γ-benzene hexachloride were associated with lower risk of scabies recurrence. Recurrence of scabies is not uncommon among elderly patients in institutional settings. Impaired immunity may be a risk factor for recurrence of scabies. Groups with a high onset rate of scabies pose a high likelihood of recurrence. Problematic behavior of demented patients may increase the risk of recurrence. Use of effective topical treatment may effectively prevent recurrence.