Are you sure the backing is cotton? You can do a burn test. take about a 1" square of fabric, hold in in a pair of tongs & use a match to light a corner. Do this over the sink with the water running. Let it burn for a second or two, then put it under running water. If there is any poly in the fabric, there will be a bump in the burned edge where the poly melted rather than burn. I haven't had an issue with cotton fabric and batting. Hopefully someone else may have an explanation.