Please though, even if you use rearguard - don't become complacent. My vet says she sees rabbits that have been 'rearguarded' still getting flystrike, because although it will kill the eggs if they are laid within a rearguarded area, it doesn't stop them from hatching elsewhere, so your bun can still get flystrike..it's unlikely that the liquid will get right into all the nooks and crannies of your bunnies 'bits' or around any wet patches or open wounds (and in fact you probably wouldn't want those chemicals getting onto skin like that!), and this is where it is more likely as flies are attracted to the damp bits.
I'm not saying don't use it - each case on its own merits - but personally I think it can lull you into a false sense of security, and believe that in healthy bunnies, there isn't really any substitute for clean dry accommodation, fly screens if possible, and daily bum checks
