I try to buy organic & all natural whenever I can, but can't always afford to that with everything. I always want the best surrounding my son's bed though, because I figure he spends 12 hours a day, every day, with his face pressed up against it, so that is an important place to start. His bed has an organic mattress, which means no plastic waterproof cover, so that needs to be protected from possible accidents. Wool was the only natural waterproofing solution. I had squares of lanolized wool, but he moves around in his sleep, so I needed more coverage... just in case. I took an old stained blanket with moth holes, felted it, lanolized it, and was able to make 3 full sized mattress protectors out of it. I think I might be selling some in my shop shortly, if I can get my hands on some more wool blankets. I had another that I was planning to use for that, but my son claimed it for his own. I think he loves wool as much as I do ;)
I purposely left it long on 2 ends, so it could be tucked in to keep it in place. I then put the sheet over the mattress protector. I usually do this in layers (mattress protector, sheet, mattress protector, sheet) for quick sheet changes. This came in VERY handy when my son had the stomach flu! Mattress protector on my son's bed:
Edited to add:
I forgot to mention all the other important benefits of wool as a mattress protector! Wool is insulated, breathable, and will wick away sweat, so a wool mattress protector will provide a more comfortable sleep (even in the summer!). Another fabulous benefit to wool is that it is dust mite resistant. This is better for everyone, especially those with allergies. Wool is also fire safe.