In much the same way that the phrase "A Sci Fi Channel Original Film" actually means "crap", the word "homeopathic" is actually a codeword for "useless". I bring this up because I'm sitting here looking at a tube of Head On (apply directly to the forehead) that has come into my hands through the capricious machinations of fate. Head On is a homeopathic preparation that allegedly cures headaches - most people know it from an series of remarkably annoying commercials that ran incessantly a few years ago. Like essentially all homeopathic treatments, Head On is a con, a way of selling people inert binders in the guise of medicine for $3 a tube.
Homeopathy is in some sense alchemy's uglier little sister. It is predicated on the twin beliefs that "like cures like" and that (somehow) the more diluted an ingredient is in a solution, the more powerful it becomes. That is to say, a material that causes, say, explosive vomiting when taken directly will actually cure explosive vomiting if taken in a very diluted form. Except for the fact that this simply isn't the case it makes perfect sense...
When you look at the package of a homeopathic preparation, you'll note that every active ingredient is a.) some compound you've never heard of and b.) is follow by a number accompanied by the letter X or C. X represents a dilution of 1 part active ingredient into 10 parts inert material, while a C represents a dilution of 1 part active ingredient into 100 parts inert material. Remember, however, that in the crazy world of homeopathy dilution = strength. Make sense? Didn't think so.
Turning back to my tube of Head On, I note that it has 2 active ingredients - kali bichromicum and bryonia alba. Some quick Google Fu indicates that kali bichromicum is a toxic chemical used to finish wood and bryonia alba is actually a poisonous plant called White Bryony. The website Plants for a Future says that eating it will cause "death within a matter of hours". Scary. And yet Head On says you can apply it as much as you want with no risk of side effects. How can that be? Let's have a look.
The kali bichromicum is found in Head On in a 6X solution. That means one part of that stuff is suspended in 1,000,000 parts inert material. That's right, one part KB diluted into a million parts of bollocks. It gets better though, because the bryonia alba is diluted to a 12X solution - one part active ingredient in a trillion parts inert suspension. And yet it gets even better, because the first ingredient is also only 0.05% of the product and the second is only 0.04% by weight. That is to say, we have this tube of junk that is 99.91% nothing, just binders, and the two ingredients that make up the other 0.09% are diluted to one part in a million and one part in a trillion, respectively. Most of a stick of Head On is actually an anti-microbial preservative called diazolidinyl urea, which is classified as a known human carcinogen according to the World Health Organization.
Check out the embedded video below to see James Randi give a much longer explanation of homeopathy, but before you laugh, remember that people are wasting money on this stuff that they could be using for real treatments.