So ask respectfully, be forceful, and stand firm. Explain that your wish that they refrain from kissing their grandchild will only persist until they are older and their immune systems are stronger. Everyone who comes into contact with your infant should practice good hygiene. This includes breastfeeding mothers, who need to express milk for their babies and then feed them the nourishing food-based liquid called breastmilk. If you refuse to kiss your toddler or baby, they might protest by hitting you or trying to hurt you in some other way. That's normal behavior for a young child who doesn't know how to deal with rejection. In this case, it is best to stay calm and ignore their attempts to hurt you. If you feel like you or your baby is at risk of getting sick, call your doctor immediately.