Most Horse repellent is not meant to be put on human skin.
Dear flies tend to go for the head first and I have worn a hat that has been sprayed with repellent.
you can also try lightweight long sleeves and spray the clothing, but most animal (horse) sprays have an oil base that may stain clothing.
Good luck deer flies are nasty persistent pests.
If you have outside dogs or cats that get bit on the ears a lot I have found a bit of Mentholatum/Vicks vapor rub keeps the flies away.
