Cold sores are common and relatively harmless in toddlers and children, but the cold sore virus can be dangerous for babies. When a child develops a cold sore for the first time, the blisters often spread beyond the lips to the mouth and gums. Occasionally a child may also have a fever, swollen and tender lymph glands, sore throat, irritability and drooling. However, if cold sores appear near their eyes, call your pediatrician. HSV-1 is especially dangerous to babies under 6 months of age because babies immune systems are not well developed until after about 6 months old. Therefore, signs that a baby may have been infected with the cold sore virus include low grade fever and one or more small skin blisters. These symptoms can occur 2 to 12 days after HSV-1 exposure. If these occur or if you have any concerns, call your pediatrician.