Why Wool?

Many people have questions about the usefulness of wool over other cloth diapering materials available. Doesn't it itch? You don't wash it? Doesn't it smell like pee? Isn't it dirty?

A high quality wool will not itch! Coming from someone who has highly sensitive skin I can tell you that most wool you have come across is not high quality. I even react to the 'non-itch' synthetic/wool blend socks that are not cheap- but can rest my cheek in bliss upon the soft smooth texture of a very fine wool fabric.
Wool that is lanolized has the unique capacity of self cleaning! The lanolin and urine in the wool react to create a 'soap' of sorts that releases impurities into the air when drying and leaves your wool soft, dry, and smelling wonderfully fresh and natural. It's hard to believe until you have tried it- and then it is always a bit amazing to see it work so well!
You will need to relanolize your wool on a periodic basis. When the lanolin gets thin on the fibers of your wool, it will not work as well and you will notice the wool becoming more damp as it's water repelling capacity decreases and it absorbs more moisture into the fabric. You know for sure it is time to relanolize when your wool does not smell heavenly pure after it dries. I recommend relanolizing your wool every 2-4 weeks depending upon how often you use it.
With wool you get the breatheability without using a petroleum product, like fleece or a polyurethane laminated polyester (PUL). Bonus eco points. Plus, being synthetic fleece retains smells when wool won't.

Marc Pehkonen wrote this article about wool:  Why Use Wool For Diaper Covers?
Wool keeps sheep dry. Why? Wool's structure produces an elegant combination of water repellence, breathability and moisture absorbency.
At a microscopic level wool consists of a series of overlapping scales (called cuticles) which have a tendency to repel water droplets. This structure, in combination with a thin coating of lanolin (an oil secreted from the sheep's skin) causes water to run off the fibers. (The duck's back effect is also a sheep's back effect.) Natural water repulsion makes wool a good candidate for a diaper cover.
But there's more. Many artificial fibers also repel water, but that alone does not make them a good choice for a diaper cover-a plastic bag would fill this condition. It is important that the fabric also be able to breathe, or the temperature next to baby's skin will rise. Breathability (and hence reduced skin temperature) is an important factor in preventing diaper rash. When a woven wool fabric is boiled, the fibers become entangled and they form a lofty mesh with many tiny air pockets. This process is called fulling. Fulled wool is a highly water-resistant, breathable fabric.
But there's (yet) more. There are artificial fibers that both repel water and breathe-Goretex is one such fabric. The third important property of wool is that it also has the ability to absorb moisture at a microscopic level. Beneath the water-repellent outer cuticle of the wool fiber is a highly porous core. The voids in this core can store minuscule water droplets-up to 30% by weight of the fiber itself-so that wool is able to both absorb and transmit moisture simultaneously. This is a very elegant, balanced mechanism, and there is no artificial fiber that can do this.
This threefold combination of water-repellence, breathability and moisture absorbency make wool unparalleled as a choice for diaper covers.
It is also worth noting that even if an artificial fiber could be manufactured that exactly duplicated the properties of wool, it would still be a less desirable choice. Without exception, attempts to mimic nature are highly energy and resource intensive, even if they achieve their goal. Simple wool keeps sheep dry. It will keep your baby dry too.