Hi Trem,
It's mentioned in the book "The Miracle of MSM: The Natural Solution for Pain 
by Dr Stanley W Jacob, Ronald M Lawrence, and Martin Zucker, Chapter 16 
entitled Pollen Allergies, pgs 161-170. The author describes a couple of case 
histories as well as his own personal experiences with allergies and MSM.
This guy is the one who pretty much pioneered the modern day use of DMSO at his 
clinic in Oregon and seems to know lots of information about MSM as well from 
treating patients in his clinic for a variety of symptoms in the last 20 years 
or so.
Hugh