Why does my puppy nip at children more than adults?

Fast, unpredictable movement combined with high pitched squealing closely matches the kind of stimulus that triggers chase behavior in a young dog, making children accidentally more exciting targets than a calmly walking adult.

A child's face, hands, and clothing sit much closer to a puppy's mouth height than an adult's do, which simply gives more opportunities for a nip to land, even during otherwise friendly play.

Always supervise puppy and child play directly, keep sessions short, and teach children to freeze and stay still rather than run if nipping starts, since running usually escalates the chase instinct rather than ending it.

Young children rarely understand the freeze instruction the first time they hear it, so practice it as a game beforehand, away from the puppy: call out freeze and reward your child for standing completely still like a statue, then bring the puppy back in once the response is automatic. Five minutes of this practice a couple of times over a weekend usually gets a five or six year old reliably able to do it under real excitement.

It also helps to give children their own calm way to interact, such as tossing a toy rather than using hands, which keeps fast moving fingers out of range while still letting them join in play. A puppy that consistently gets a toy thrown for it around children learns to associate them with a game that does not involve teeth on skin.

If nipping around one particular child keeps recurring despite supervision, shorten those sessions further, to two or three minutes at a time, and end each one before your puppy gets overexcited rather than waiting for a nip to happen first. Ending on a calm note, before arousal peaks, teaches the puppy that calm play continues while wound up play gets cut short.