A long time ago, my parents stumbled across the medicinal properties of Goldenseal. Last year, during the rainy Oregon winter, a 1/2 feral litter of kittens started trying to find shelter on my porch. Not long after they started coming around, the mother left them (went into heat i assume) and came back with a hellish upper respiratory infection. She proceeded to spread it to the whole litter. I had no money to take them to a vet, and they were dying of it. I wasn't sure if the Goldenseal would be poisonous to them, but I figured they were so bad off, it was worth a try. I used the liquid extract, started small, maybe one dropperfull to two cans of wet food, and eventually raised it to 3 droppersfull (between 1 adult and 5 3-4 month old kittens). They improved from even the smaller amounts, and improved drastically from higher dosages. Although for those that couldn't smell the wet food, i had to mix a few drops in canned salmon or tuna juice to get them to eat it. It didn't harm them. I swear by the stuff now, and have used it on my own indoor cats (though I've never gotten them to take it without forcing them.) Everyone should be aware that goldenseal doesn't just work on humans.
I took the tip from someone on this site to put ACV on the scruff of my cat to help with a respiratory infection, and not only did it help her condition a bit, her whole coat has become magically lush. I don't know if it was spread everywhere from us petting her or brushing her with a baby brush, or if it was absorbed through her skin and spread from there, but wow. She was always a scruffy runt, but now she's downright regal looking!