If you have a foam bed pillow, you know how it naturally sustains its shape. Foam pillows are also allergen resistant, which is great for allergy sufferers. You should replace your foam pillow every 2 to 3 years. The foam will begin to break down at this time from regular use, which will cause it to lose its fluffiness and allow allergens to get into the cracks in the foam. To help fluff it and keep it clean, wash your foam pillow once a month in the washing machine on the gentle cycle, and completely dry on a low heat dryer cycle.