Small blisters around the child’s mouth that are in clusters and are painful and itchy are most likely caused by herpes simplex virus infection and can be treated with antiviral therapy. Depending on the age of the child, consider whether to apply acyclovir ointment to the affected area, or visit the pediatrician for a prescription medication. If the child does not have a viral infection, it is also likely to be an allergic infection. Allergic infections are most common during childhood, such as eating eggs or coming into contact with poor quality items, such as poor quality toys, can cause ulcers and blisters at the corners of the mouth. There is also a case of corns of the mouth caused by malnutrition in children, mostly due to vitamin C deficiency, which can be replenished in time by taking vitamin C tablets orally, or by eating plenty of fruit.