It has been shown that dirty sand can carry mold, bacteria and many parasites, such as pinworms and toxocara, which are all very dangerous to the health of your child. It is highly recommended that children not play in boxes that have a clear indication of soiling or contamination, and that they thoroughly wash their hands after use. We suggest that you keep your kids sandbox covered when not in use. Also, the sand in your box should be changed regularly. Many of our products come with ultra-fine, hygienic sand.