I googled it and here is what it says:
Microsafe Batting 100" Wide. This batting is an extremely fine denier polyester fiber with a dense cross-link pattern. The bond strength is unsurpassed, the insulation excells, the hand is soft and silky. This fiber will withstand the most rigorous washings. MicroSafe fiber provides continuous control of the growth of bacteria, fungi, mold, mildew and yeast. MicroSafe creates clean, sanitary conditions, making it ideally suited for bedding products. The elimination of microbial growth reduces odors, staining and textile product degradation. MicroSafe is very safe and will not wash out. Hypoallergenic.