Acyclovir is a common antiviral medication often prescribed for children to treat viral infections like cold sores and chickenpox. As a parent, it's important to know that this medication is generally considered safe for children when administered at the correct dosage. Your child's doctor will determine the appropriate dosage based on their age, weight, and the severity of the infection. Some possible side effects of Acyclovir include mild symptoms like nausea, diarrhea, or headache, but more serious reactions can occur. Always consult with your child's doctor if you have concerns or if your child experiences any unusual symptoms while taking Acyclovir.