A mattress protector is an item of removable bedding that sits on top of, or encases, a mattress to protect it. It is a must have accessory with any mattress. Common causes of the mattress getting dirty are: Body sweat / perspiration Dust accumulation on the mattress Bedwetting accidents in case of younger children or the elderly. A mattress protector acts as a barrier preventing any liquids / dust from seeping through, while at the same time allowing the mattress to breathe thereby keeping it cooler. Also since they are machine washable they are very easy to clean and can be used year after year.