Primary herpetic gingivostomatitis is a frequent problem in pediatrics. Complications of this are dehydration, pain and hospitalisation. The objective of this randomized controlled trial is to assess the clinical efficacy of oral Valacyclovir to decrease the duration of symptoms associated with acute herpes gingivostomatitis in children. This study will involve 80 children aged 1 to 8 years old to receive weight adjusted doses of valacyclovir for 7 days. The primary outcome measure will be the duration (in days) of feeding and/or drinking difficulties.