This is such a strange question.
DD just turned 5. Cold season is here, which means we once again get to see her licking her runny nose. Not below her nose, but the whole way around the nostrils. Kind of like a dog. It's pretty disgusting. I've never seen DS, 3-1/2, do this. Little kids are proportioned so differently, and I don't know if this ability is just something she'll grow out of or something she'll have to learn to stop doing. We have tissue boxes all over the house and she knows how to use them, but it's obviously so much easier for her to lick her nose clean. I hate to make a big deal of it because then she'll do it to get attention or irk us. Now, luckily, it's just to get her nose clean. Do any of your kids do this?