Depends who you ask.
The American Dental Association released a statement last week warning parents that
dental decay-causing bacteria can be transmitted from adult to child by sharing eating utensils, or by the parent sucking a baby's pacifier clean.
The warning comes on the heels of a recently published study in the journal of the American Academy of Pediatrics, about the immunological benefits of adult saliva.
The study said that parents can transfer lots of good bacteria to their infant by sucking the pacifiers clean.
"Parental sucking of their infant’s pacifier may reduce the risk of allergy development, possibly via immune stimulation by microbes transferred to the infant via the parent’s saliva," the authors concluded.
But don't swallow that story whole, says the American Dental Association. Licking a pacifier, as promoted in the study, can transfer the cavity-causing bacteria from the parent to baby increasing the possibility of tooth decay as they grow, the ADA warned.
"A child's teeth are susceptible to decay as soon as they begin to erupt," said Dr. Jonathan Shenkin, a pediatric dentist in Maine and a pediatric dental spokesperson for the ADA, in a press release. "Cavity-causing bacteria, especially Streptococcus mutans, can be transferred from adult saliva to children, increasing their risk of getting cavities."
Dr. Shenkin points to other steps that parents can take to help children develop a healthy immune system. "Breast milk is widely acknowledged as a good immunity-builder as well as the most complete form of nutrition for infants. This is something on which both the ADA and the AAP agree," he said.