My 5 mo baby girl's left eye is watery at times. could it be due to cold? no other symptoms. she is active otherwise.

Possible tear issue: A small group of infants have an obstruction to the lower portion of the tear drainage system (inside in the nasal passages). Since the tear overflow is on one side only, this is a possibiity. It can also occur from disease in that eye. Best to have your pediatrician look at this and he/she will refer the child to a pediatric ophthalmologist if needed.