I was sitting outside today reading to my daughter and there was a fly that would not stop biting my legs. It was really driving me nuts. Then I thought about something I'd read in the past to keep flies away. I got up, went to the garage and lightly sprayed my legs with WD-40. I don't know if it's the smell, the taste, or the 'oiliness' that they don't like, but there was no fly bothering me after that.
I'm thinking that this could be put to good use on a cow or a horse to help relieve them of some of their summertime miseries. AND I've read that there's nothing in WD-40 that is harmful if swallowed. Pretty cool. So spray it on a rag or your hands and wipe it on your animal's face... or your legs and arms or wherever to keep the pesky flies away!