As many of you may have heard — I believe merino wool is an optimal clothing material. But it is also useful in the bedroom: as an optimal comforter fill. The advantage of wool is that it doesn’t retain moisture. Wool absorbs up to 30% of the moisture and diffuses into the room’s atmosphere. Thus you don’t feel wet and clammy. Synthetics can only absorb moisture up to 4% of their weight.
Studies by the Ergonomics Unit at the Polytechnic Institute of Wales showed that one’s heart rate is lower while sleeping under a wool-filled comforter (compared to a polyester-filled comforter).
This also means wool comforters do not attract dust mites, which require moisture to live.
Moreover, the down used in comforters often comes from questionable sources, and it is prone to picking up dust mites and lint. In my experience at the labs, down comforters often release feathers that eventually scatter across your bedroom.
I am slowly replacing my down comforters with organic merino wool comforters.