Contrary to what you may initially think, grease lice are not actual lice. Grease lice is a yellow-gray, oily, often sticky substance left behind in the washing machine. Often this is a combination of dander, grease, detergent and hair. It causes your laundry to smell, even after it has been washed. Because grease lice are a breeding ground for bacteria, your laundry won’t clean as well. There are several things you can do to prevent grease lice; wash hot once in a while, rinse extra, don’t use too much detergent, leave the door open, wipe the rubbers (e.g. of the door) regularly and keep an eye on the filter.