This 1-year multicentre prospective study in northern France sought to evaluate the incidence of secondary bacterial skin complications related to varicella, describe these superinfections, and analyse risk factors for their onset. The study included every child admitted to a district paediatric unit with a varicella infection. Patients with varicella infection, with and without secondary bacterial skin complication, were compared. The study included 159 children, 43 of whom had a secondary bacterial skin complication on admission, 21 of them had a severe secondary bacterial skin complication (respective incidence: 7.5 and 3.7/100,000 children younger than 16 years old). Persistence or recurrence of fever > or =38.5 degrees C for > or =3 days after the beginning of varicella infection (adjusted odds ratio (aOR)=8.1; 95% confidence interval (CI): 2.3-28.4) and the use of non-steroidal anti-inflammatory drugs (aOR=4.8; 95% CI: 1.6-14.4) were independent factors associated with severe secondary bacterial skin complication.