Is there any research on using WD-40 as a fly spray for horses?
WD-40 is a petroleum based product and is NOT safe to use around animals. Here is their MSDS safety sheet: http://www.wd40company.com/files/pdf/msds-wd494716385.pdf
It's well known that WD-40 is NOT SAFE as a skin topical. Do not use it except for its intended purpose (which, BTW, is not as fly spray.)Just buy fly spray. It's only a few bucks.
I believe it has methanol in it wich is poisonous,
WD-40 would make lousy fly control. Buy cheap fly spray and add a couple of ounces of running alcohol