Sphagnum moss can contain a fungus that can effect some people. It is quite rare, but caution should be used when handling it. Perlite is a heated natural mineral, and is often used as an additive in potting soil to help retain moisture and give an airy texture to the soil. It is also used to mix with many of the potting mediums for orchids. I use it with my bark, which helps hold a little more moisture.
Some growers even use it alone with great success.
Some of the advantages of perlite is it does not rot, therefore thrips or fungus gnats will not infest the medium. All epiphytes that can be grown in bark can be grown in perlite. You can buy different grades from very fine to coarse. Charcoal helps to keep the mediums sweet and keeps them from souring. You can buy charcoal in large and fine grades.