Using loose substrates for geckos poses significant risks, particularly impaction, where ingested substrate material obstructs the digestive tract. This can lead to serious health issues, including blockages, constipation, and even life-threatening complications. Young geckos are especially prone to accidentally ingesting loose substrates like sand or small shavings while feeding. Specific loose substrates can also harbor bacteria and parasites, potentially leading to infections. Therefore, it's advisable to use safer alternatives like reptile carpets or butcher paper to minimize these risks.