Synthetic comforters are filled with polyester, a 'down-alternative'. Steady improvements in the manufacture of polyester have created fills that share many of the qualities of down with one significant advantage-they are hypoallergenic. As down degrades over time it produces dust to which some people are allergic. Down is made of keratin, a natural protein that is food for dust mites. Dust mites are also a primary cause of allergies. Denier is the term for a fiber's thickness. High-quality goose down is .5 denier. By comparison, human hair is approximately 50 denier. Any fiber of less than one denier is considered a microfiber and it is now possible to produce polyester fibers that are no thicker than goose down. Synthetic comforters with high-quality polyester fill and high thread-count shells are warm, comfortable and easy to care for. Primaloftİ, a branded synthetic fill, feels and performs like premium goose down by mimicking the characteristics of down clusters more closely than any other fill. Completely hypo-allergenic, Primaloft far surpasses other synthetic fills for loft-retention, warmth, and durability.