That was probably me! done it for years, don't have a problem with sweet itch, or horse flies.
I'm sure I've read somewhere that garlic is toxic?!
On equisearch maybe?
garlic in their feed, vinegar is good as a fly repellant just slap it all over your horse only seems to work for an hour or so tho so ace for riding but they stink!
garlic can make itchy horses more itchy if fed too much, i think its because it boosts the immune system therefore the reaction that some horses get to fly bites gets worse? my horse has sweetitch so i feed him marmite, not convinced it works mind, apparently works on people too!
jakesmydog, regarding your comment about garlic being toxic, I read that for garlic to have an effect and repell flies you would have to feed it at toxic levels. i still feed him a scoop a day though, its in my head he needs it..