Cat's purr has healing powers

[snopes]

Comment: I've heard before that cats' purring has healing powers. After a
bit of web surfing, I've found several articles that say this, and in
particular that the low-frequency sound improves bone density and bone
growth. Several of these articles point to the "research" of of the Fauna
Communications Institute .

That site is pretty suspicious. The president of the institute, Elizabeth
von Muggenthaler, doesn't seem to have an advanced degree, although she
calls herself a bioaccoustician. Her arguments for the healing power of
purring http://www.animalvoice.com/catpurrP.htm don't seem sound. And in
fact, they do read more as arguments than as science (scientific studies
are written in a disinterested voice, and they present their hypothesis
and then demonstrate whether the study confirmed or disproved the
hypothesis).

Anyway, I suspect that the various articles that say that people have
found that purring can heal are all referring directly or indirectly to
this one, unauthoritative site. Here's an example published by Scientific
American: http://www.sciam.com/askexpert_quest...FC809EC5880000
that contains no references.

I haven't found anything that references a more authoritative study