Nervous about using horse meds....

So I did just buy a thing of "Exodus". There is no doubt I'm still infested and fed up, however the last time I took " parasite free" which was a blend of herbs he die off was so bad I couldn't move the next day, or talk was so sick. Took days to recover. This was like 2 years ago probably.
I am also worried about the side effects from a horse medication. My liver is still sluggish, don't want to poison myself. It says on the side " Do not use in horses for human consumption". Why does it say that?
Is there a die off-reaction? Will it do any other kind of damage? I want these things gone, but dont want to damage myself in the process. Any and all help would be much appreciated. Tweet