You might think moms who don’t let their kids play in a sandbox are of the paranoid variety. Heck, I used to scoff at them at the playground, while my tot gleefully shoved sand down his pants. But then I came across this NSF International study while writing about the germiest places for kids. I learned that public sandboxes top the list by a mile, and I promptly became a card-carrying member of the no-sandbox club. So much so that my 6-year-old will yell, “No!” to stop my 2-year-old from venturing into the sandbox at the park.

For those who still aren’t convinced, here’s a taste of the menagerie of diseases your child can catch from a sandbox.

1. Toxocariasis. Sandboxes are giant litter boxes for a passing animal. Think of it as a cat/raccoon/dog/rat porta-potty. And much of this fecal matter can contain toxic bacteria, one of which is called Toxocara, also called roundworm. A Japanese study, which used a camcorder to videotape public park sandboxes, found that cats pooped in the sandboxes “habitually” and the sandboxes themselves were contaminated with Toxocara eggs. Infected animals secrete these parasitic eggs with their feces, which then take two to four weeks to turn into larvae. Humans can become infected by ingesting Toxocara eggs, which can happen easily when a child plays in an infected sandbox and then (gulp), touches their mouth. Once inside the human body, the eggs hatch and the larvae use our bloodstream as an interstate, traveling to our major organs and possibly causing damage. Some infected people experience no symptoms, but others experience devastating ones such as liver or heart failure, or loss of eyesight.

2. Baylisascaris. This parasite (often referred to as raccoon roundworm) is particularly dangerous, since there's no known effective treatment and infection can cause permanent brain damage or death. The eggs of this parasite are found in raccoon feces, which can be deposited into a public sandbox by a passing raccoon who mistakes it for a bathroom.

3. Pinworms. I’ve gotten the dreaded letter from my kid’s preschool at least three times. Someone in my child’s class has been infected with pinworms. They are quite possibly the nastiest parasite I can think of because they don’t just stay in a child’s body. They travel down to the child’s anus to lay eggs at night. If your child is suddenly scratching his tush an awful lot, suspect pinworms and seek treatment. This is transferred easily in a sandbox: Infected child A scratches his tush absentmindedly while he’s building his sandcastle. Child B comes to join in the fun, puts his fingers in his mouth and picks up more than he bargained for.

Still, many doctors say to relax. “Everything on a playground is hazardous and one needs to pick and choose what is preventable from what is not preventable,” says Dr. Melissa Sheinker, a pediatrician in Boca Raton, Florida. “As long as a parent or caregiver is wary and does their best to wash a child's hands after playing in the sandbox, then they are actually quite safe.” A little common sense will go a long way, though. “Of course the parent or caregiver should also make sure they aren't eating the sand while playing or sticking their hands or any of the sand toys in their mouth while exploring the wonders of a sandbox,” she adds.

The risks of getting these infections is relatively small, which is why sandboxes are still alive and well today. Indeed, as Sheinker puts it, “The likelihood of a bad elbow fracture from falling off a set of monkey bars is much greater than the likelihood of a parasitic disease from a sandbox.”

You may decide that the benefits of this calming, outdoor play outweigh the risks. Suit yourself. I’ll stick with the swings and the climbing wall.