“Kissing your baby changes your breast milk. Did you know that the undeniable urge to cover your baby in kisses serves a biological purpose? When a mother kisses her baby, she samples the pathogens on baby’s face, which then travel to mom’s lymphatic system. Mom’s body then creates antibodies to fight those pathogens, which baby receives through breast milk. What?! Amazing, right?”
https://www.mothering.com/threads/10-things-you-might-not-know-about-breastfeeding.1623996/