First of all, I want to make it clear that the words "homeopathy" and "holistic" are not interchangeable.
Holistic, an adjective, can be tacked onto any noun. It's a lot like "natural" or "organic"-- used to the point where it's been stripped of a lot of its original meaning. Holistic doesn't mean holy or arcane or even more natural; it simply means taking the whole into account.
Homeopathy is a branch of alternative medicine which is based on the concept that highly diluted amounts of certain molecules (depending on the disorder) can stimulate the body to heal itself. A lot of people (including the ones who contributed to the Wikipedia page on homeopathy, linked above) dismiss homeopathy on the grounds that it's pseudoscience or completely refutable.
I am not a firm believer in homeopathy, but I do not deny the possibility that it could work on some unperceived level. Mostly, it reminds me of desensitization therapy for severe food allergies. Also called oral immunotherapy, it is what it sounds like: desensitizing the immune system to an allergen by administering it sublingually in extremely small doses. It's kind of a stretch to try to make any solid connection with that and homeopathy, though, so I usually keep my mouth shut when the subject of homeopathy comes up.
Today, though, I read this article and was pretty surprised. Apparently, homeopathic medicines actually have nanoparticles of the diluted substance in them; a few Nobel laureates are really into homeopathic research; and hormesis, a widely accepted field of science which studies the effects of small doses, exists! This collection of writings on hormesis and homeopathy was also originally published last year as a special issue of Human and Experimental Toxicology.
The article I linked to explains everything way better than I can; I wanted to mention it here because I think that it could have a lot of implications for/involvement with the immune system and the microbiome. It could be some crazy electromagnetic sub-cellular language. Or, it could be complete quackery. I guess time will tell, but one thing's for sure: funding for that kind of research will be pretty scarce, especially here in the States.
