hi ,horse flies at the allotment are huge,and as far as injecting anaesthetic these have run out i can feel the thing stick me, not far of a wasp sting pain and i used to be covered with red lumps that lasteed days if you scratched them,i was quite often left with spots of blood where they hed been,now i use one of two things Tesco insect protect,,and it works they dont like it ,and a lady gave me some ,,avon skin so soft cream and beleive it or not that works for Kate my partner and me, the Tesco one smells of citronella but the other is more feminine smell and the horse flies dont like it and have stayed away from me,,good luck