If one of your kids has pin worms, you'll know it. They'll have trouble sleeping as that's when the worms work their way out of their bottoms to lay eggs. Your child will complain that it's itchy and it will drive them crazy. The pin worms are acquired by direct fecal/oral contamination. What I mentioned about the faucet in my earlier post is the most common way kids get it. It is an intestinal parasite that leaves the body at night via the rectum to lay eggs. The eggs get transferred to the child's fingers when scratching, wiping their bottoms, what have you. Then they touch something else with their soiled fingers. Someone else touches that thing then puts fingers in mouth, or something that child touched in their mouths. The eggs are swallowed and hatch somewhere in the digestive system (bowel maybe...can't remember), then the whole thing starts again. The only way that I know of to get rid of them is from a doctor's prescription meds. I don't think they're caused from sitting on the ground or dirty places. I'd be very surprised if that was the case since it's an orally acquired problem. The stuff you're doing now is just right. Don't worry too much about it. As long as the child's hands are clean and you don't see any diaper archaeology going on, it's not likely to effect you.