sulfur (yellow) salt blocks for flies?

[springer]

I was told that these salt blocks are good for discouraging flies. Any experiences with them? Can they be harmful to a horse in any way?

[LexInVA]

For your intended purpose, there is no empirical evidence that supports the belief that they do anything to discourage flies. They are no more harmful than any other salt block I suppose but you should just use what your horse needs for it's dietary requirements per your vet or whatever you use to gauge their needs.

[luvmywalkers]

For what it's worth: None of my horses licked theirs - and they all love their salt.

[jaimebaker]

I fed sulphur blocks for years. Didn't notice any discouraging of bugs though.