Ask the Doctors: Are sandboxes breeding grounds for bacteria?

Dear Doctor: My sister-in-law read that sandboxes are full of germs, and now she won’t let her kids play with my sons in our backyard. I can see how a public playground might be less than clean, but isn’t she overreacting by putting my yard off-limits?

Dear Reader: It’s possible that your sister-in-law is reacting to the results of a small study from Spain, which made a bit of a splash last summer. Researchers in Madrid tested the sand in 20 public sandboxes for children and 20 public sandboxes for dogs (who knew?) and found that both types of sandboxes were hosting a nasty bacterium called C. difficile, or C. diff.

Nine of the 20 children’s sandboxes contained the pathogen, and 12 of the 20 dog sandboxes had it as well. Most commonly seen in nursing homes and hospitals, where it can spread from patient to patient, C. diff causes an intestinal infection that sometimes leads to severe diarrhea. Some of the C. diff strains in the Spanish sandboxes showed increased toxin production, and some were resistant to antibiotics, which are the primary form of treatment.

But this study isn’t the first to point out the risks of sandboxes. By their very nature — exposed to the potentially dirty hands, feet and bottoms of multiple children, and available to insects and animals — sandboxes are a likely breeding ground for all sorts of unpleasantness. This includes bacteria left behind by human contact, as well as common parasites like roundworm eggs and hookworm larvae from the feces of infected animals.

While this all sounds quite dire, there are steps you can take to make your backyard sandbox safer, and to protect your children in whichever sandbox they use.

For your home:

— Keep the sandbox covered when not in use. Whether you use a tarp or a wooden cover, it’s important that the fit be tight. Cats, rats, mice and raccoons prefer a dry place to do their business.

— If the sand gets wet during play, be sure to let it dry thoroughly before covering. Molds, yeasts, bacteria and other unhealthy things love a moist environment.

— Replace sand regularly. Be sure to use play sand rather than construction-grade sand, so it will not contain silica.

— Rake and sift the sand frequently to check for debris. If you find any scat, you have to assume the entire box is contaminated. Dig it all out and start fresh.

For your kids:

— Make it a rule that they wash their hands before and after playing in any sandbox.

— We’re sorry, but with younger children you’re going to have to keep an eagle eye to make sure hands — and sand — don’t get into the mouth.

— Wash and disinfect any and all sand toys your kids use. It just takes a minute and makes a big difference.

— Clothes that have been in the sandbox should head right into the washer. Shoes should be thoroughly brushed clean.

It sounds like a lot of work, but depending on how your kids feel about the sandbox, it can be worth the effort. And who knows? Your sister-in-law may even relent and let her kids come over.

Eve Glazier, M.D., MBA, is an internist and assistant professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and primary care physician at UCLA Health.