I don't know if this is too far fetched but I once had a great dane which almost died of demodex, which is a skin mite which is normally harmless for most dogs but for my dog, it was supposedly fatal. I was about to give up on her (both parents and 1 sibling that I knew of were put to sleep, it was severe) when a health store owner advised I overdose her on Echinacea/goldenseal. Well, it was so long ago, I think I would give her 6 tablets per day! Believe it or not, she went from almost dead, infection weeping out of everywhere including her eyes, bald, almost unable to get stand anymore, to perfectly fine in about 2 weeks. Have you tried that particular herb? It might be worth a shot! I know if saved my dogs life and the infection which all the vets said would come back never did come back. The healthstore owner advised that I give her that particular herb, bath her with a tea tree oil shampoo and take her off dog food since it had too many byproducts so that's what I did. I know that your issue is with parasites but demodex is a skin parasite so maybe it will work for you in the same way. I have added it to my daily supplements lately, since I remembered that experience but since I don't have the severe reaction your having, I'm only taking 1 capsule a day.