A doctor has now released a video explaining why you should be buying new pillows every two years! He says ’You need to change your pillows at least every two years because “The average person sheds about 4kg of skin every year. Most of that ends up on your bed or pillow – a feast for microscopic dust mites. “A single dust mite has about 20 droppings each day, multiple that by the hundreds of mites living on your pillow. Yummy.