Acute facial nerve palsy occur in 10-20/100 000 children/year in Sweden. About 20 % of these children will have persistent symptoms with excessive tear secretion, drooling and social problems due to asymmetry in the face. Studies on cortisone treatment to adult patients with acute facial nerve palsy have shown beneficial effects, but no studies with strong quality have been performed in children. Investigators will perform a double-blind randomized placebo-controlled multicenter trial on children with acute facial nerve palsy. Participants will be recruited consecutively at 9-12 study centers in Sweden during 2019-2020. Oral cortisone (prednisolone) 1 mg/kg x 1 in 10 days (or placebo) will be started on admission. Clinical data, including recovery will be followed-up until 12 months. The primary outcome is defined as total recovery of the facial nerve palsy, measured with the House-Brackmann scale (grade 1) at 12-months follow-up. The overall purpose is to assess the utility of cortisone treatment given to children with acute facial nerve palsy in this study. If the total recovery rate is significantly improved in the prednisolone group as compared to the placebo group, prednisolone treatment will be introduced in clinical practice for children with acute facial nerve palsy in order to reduce the risk of persistent symptoms.