Silk contains a natural protein called sericin and 18 other amino acids which are similar to those in human silk, which makes silk mold and mildew resistant. For those kids who tend to be allergic, silk filled bedding has the least opportunity to provoke reaction.
Petroleum-based products like polyester are detrimental to the environment on many levels. Silk is considered eco-friendly for a variety of reasons. First and foremost, silk is renewable source. Second, ecological footprint of resource- not much natural resources (land, water or other natural material) required to bring the silkworm to full growth and develop the silk from cocoon. The third, no chemicals it requires to grow and process silk floss to make it ready for market.