Ingesting small amounts of potting soil is generally not harmful to children, as it is made of organic materials such as peat moss, perlite, vermiculite, and compost, which are non-toxic. However, it's important to keep in mind that potting soil may contain harmful bacteria such as E. coli or Salmonella, which can cause gastrointestinal problems if ingested in large amounts. In addition, potting soil may also contain fertilizer, pesticides, or other additives, which can be harmful if ingested in large amounts.