Fleas and Lemon Juice

I've heard lemon rubbed on the fur of animals will deter fleas, any truth to that? Also would it be the oil or the juice if this is accurate?

I think you are referring to the "Lemon Lotion" recipe cited by Juliette de Bairacli Levy in her book, "The Complete Herbal Handbook for the Dog and Cat". In this recipe she refers to using lemon halves (24 halves to one gallon hot water). She talks of letting the mixture sit in the sun until the lemons become mouldy. Squeeze and remove the lemons, replace with 24 more halves and repeat the process. Once the second set become mouldy, squeeze and remove. She says to rub the lemon lotion into all parts of the dog's body (she refers specifically to dogs) in order to expel fleas and other "skin vermin".