BACKGROUND: Little is known about the impact of ultraviolet exposure, climate factors and pollutants on pemphigus. AIM: To determine whether these factors are associated with pemphigus exacerbation resulting in hospitalization. METHODS: The analysis used data from the 2002-2012 National Inpatient Sample in the USA, including 68 476 920 children and adults, and measurements of relative humidity (%), ultraviolet (UV) index, outdoor air temperature and particulate matter of