One method of making down more allergy-friendly involves subjecting actual birds' down to repeated washing and rinsing to remove dirt, dander and dust mites from the feathers. This treated down is often encased in hypoallergenic fabric, which has been so tightly woven that potential allergens cannot penetrate the fibers. The result is not completely non-allergenic, but does have much less tendency to produce an allergic reaction.
Many companies produce down alternatives made of various types of synthetic materials. Some of them use resilient, gel-like polyester fibers that are manufactured to mimic the springiness of natural down. Another down alternative used mainly in the manufacture of hypoallergenic pillows is to surround a foam-rubber core with finely-shredded synthetic foam; the shreds provide loft and the "sinking into comfort" feeling of down, while the core supports the head.
Down/ Syriaca Combination
Hypodown is a combination of hypoallergenically treated down with Syriaca, which is the fluff from the pod of the milkweed plant. The milkweed fibers are thought to trap and bind dust and dander, thereby suppressing dust mites and other allergens. It is also said to have superior durability and warmth than pure down. This combination down alternative is usually made up of 85 percent down and 15 percent Syriaca.
Silk or Wool
In the case of specific feather allergies, silk or wool fibers can provide alternatives to down. Alpaca wool is softer than regular sheep's wool and is naturally resistant to dust mites, mildew and mold. Mulberry silk strands are comparable to down in softness, insulation and comfort, and pillows filled with silk are advertised as being "naturally hypoallergenic." Both silk and wool fibers will shift and bunch like down.
Down alternatives---whether hypoallergenic or not---are often much less expensive than quality down-filled items. They are also easier to care for and to launder. In addition to their obvious advantages when used by people with allergies, down alternatives are also thought by some to be a "greener" choice, since birds are killed to harvest the down while synthetic materials---and renewable resources such as wool and mulberry silk---are considered cruelty-free.