Can kittens have 1 percent milk?

Except in the case of immediate emergency with no other option, it does more harm than good to give cows' milk to kittens. Kittens should get their mother's milk until weaning; if the queen isn't producing sufficient milk or is otherwise unable to care for the kittens, you should feed the kittens a formula designed for cats (e.g. KMR).

After weaning, cats have no need of milk and it shouldn't be given to them. Most cats are lactose intolerant, so even 1% milk can cause serious problems.

That being said, an accidental lick or two by a curious kitten shouldn't do any permanent harm.