Neem oil.
I bought a large container last spring and still have about half left. I use it for fly control on horses, on the dogs as it stops fleas and ticks, on the chickens for red mite, on the garden for slugs, snails, fungal infections, and other plant feeding insects.
It does stop itching and as it stops flies and gnats it helps with sweet itch.
With the latter I also feed NAF D-tox as this alters the horse's immune system.
I soften the neem in hot water as it solidifies, 5ml of neem, 3 ml of shampoo, add 1 litre of hot water and swab that over the horse. It will remain in them for a week or more.
