Research indicates that your pillow probably houses more than a million spores of up to 16 kinds of fungus:

“Open up an older pillow and it’s a cesspool of mold, mildew, fungus, dust mites and mite feces,” said bedding expert Dan Schecter. …

“The conditions for fungal growth are so perfect: We put 20 gallons of sweat into our beds each year.”

So, using a grant from England’s Fungal Research Trust, [Ashley Woodcock, professor of respiratory medicine at the University of Manchester in England] examined five feather and five synthetic pillows. His findings, published in the Allergy journal, showed what Woodcock called a “miniature ecosystem” at work within both types, with dust mites eating fungi, and fungi using mite waste as a source of nitrogen and nutrition. …

New research shows pillows may be a breeding ground for fungal spores, which could aggravate allergies or asthma. To help reduce problems:

• Use a breathable, moisture-repellent pillow cover fabric, such as Gore-Tex.
• Wash pillows at least four times a year.
• When laundering, wash on the gentle cycle, two at a time.
• Fluff the pillows halfway through the dryer cycle to prevent lumps.