I remember when I got my first package and being like, "huh?"
However, as I used the product, and as I really thought about how much waste typically occurs with supplements (bottles, little seals of freshness, big chunks of cotton, not to mention any boxes that might contain the bottle) I really dug the simplicity.
If you want something "catchy" come up with an envelope design that has some information on it, with some nice logos, and maybe one of your catchiest stories.
Granted, some people would want to "brown bag it" but I spread the news as much as I can, so the more people who read it along the way, the better it is all around, in my opinion.
OR! have you seen the book Stupid Sock Creatures?
http://www.stupidcreatures.com/gallery.html
or seen the Ugly Dolls merchandise?
http://en.wikipedia.org/wiki/Uglydolls
Maybe you can come up with an envelope design that has cartoonistic parasites in repeating colorful squares.
I saw something like the ugly doll brand of wrapping paper-- and I tried to find it online (I'd seen it in a Borders store.) No luck.
but this seems like a fun and colorful way to spice things up if you're bored, and to still retain relative "brown bagness" of the contents.
Plus, we all like showing off our parasites (or we must as I keep seeing the same posting ad nauseum: "HW, what's this?") Imagine having us send in cartoon sketches of our "Punky Parasites." I could see that being really popular with adult posters and their children :D
And-- you don't have to send everyone those envelopes (just me :D) You could randomize it since you have a lot of repeat clientele. It'd be like the golden ticket. I know I'd save my envelopes (if they were cool enough)...so that also eliminates waste and justifies a bit of the added cost.
I also think anything artistic like this helps some of the frustration and grossness of having a parasite. It's like our own CZ version of "The Snorks"-- weird looking creatures just looking for a home in a dark liquid environment. What happens to these plucky parasites as we shoot them off into unknown "space"?
http://en.wikipedia.org/wiki/The_Snorks