Construction and parts
Internally, a pillow consists of a filler, often made from foam, synthetic plastic fibers, feathers, or down and viscoelastic foam and latex. Traditionally straw was a filler, but this is uncomfortable and rarely used today. Feathers and down are the most expensive and usually the most comfortable; they offer the advantage of softness and their ability to conform to shapes desired by the user, more so than foam or fiber pillows. One of the disadvantages of a down-filled pillow is allergic reaction of the user. There are currently hypoallergenic varieties of down pillows to allow people sensitive to down to enjoy the comfort of feather or down pillows. In Asia, buckwheat is a common filler, as are plastic imitations. Such pillows tend to be smaller than a standard pillow. In India, cotton is also a common filler.
The fill is surrounded with a cover or shell made of cloth, such as silk, known as the pillow case or pillow slip. Some pillows have a fancier cover called a sham which is closed on all sides and usually has a slit in the back through which the pillow is placed. Rectangular standard bed pillow cases usually do not have zippers, but instead have one side open all the time, however, a zippered pillow protector is often placed around standard pillows with the case in turn covering the protector. It is recommended that all types of pillow covers be laundered periodically since they are the part that is in contact with a person’s body. Pillows tend to accumulate dust and microbes among the fill, even when washable pillows are washed. Manufacturers recommend tumble-drying for fifteen minutes every week to freshen them up, and for the heat to kill dust mites. The normal lifespan is two to four years.