According to Dr Arthur Tucker, principal clinical scientist at Barts’ vascular unit, up to a third of the weight of your pillow could be made up of bugs, dead skin, dust mites and their faeces.

(In fact, up to 100,000 dust mites could be having a party in there right now, and you don’t want to think about hospital pillows, which can have more than one million Staphylococcus hominus per millilitre, and what about hotel pillows! On a more positive note, leading bacteriologist Professor Hugh Pennington said not to worry as your pillows at home simply contain the bugs we already have. Well that’s alright then – party on dudes.)

Factoid Source