Not much. Many 4-year-olds are quite affectionate and will frequently hug and kiss one another and relatively unfamiliar adults. If they are from affectionate families, they will definitely do this when “playing house” at school. You didn’t indicate whether your child was a boy or a girl, but this kind of behavior is a little more common in girls than boys. Girls are more likely to be the roaming kisser, and they are less likely to resist being the recipients of hugging and kissing than boys are. Teachers usually handle this behavior very casually unless a child is annoying other children. If so, she will say something like, “Kevin, Jenny doesn’t like it when you try to kiss her,” or “Jenny, some children don’t like it when you force a kiss on them.”
Unless you hear from the teacher that your child is frequently annoying the other children with this behavior, I wouldn’t do anything. If she thinks your child is losing friends because of it, she herself will develop a strategy for reducing the frequency—noting whether your child is kissing just one or two people or most of the children, what is happening in the group when it occurs, etc. As she works to isolate the kinds of situations that lead to the kissing and maneuver the situation so the opportunities don’t present themselves, she will undoubtedly want to talk with you to make sure the two of you are on the same track in your attempts to reduce or eliminate the behavior.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.