Pharmaceuticals are investing a hell of a lot of money in finding the active components to a lot of "natural" medications. Take, for instance, licorice root. In traditional Chinese medicine, it has been used to control gastrointestinal disorders such as stomach ulcers, whereas Western herbalists tend to use it for a more varimore varied array of disease processes, some of which are justified by science, others which are not.
It seems strange to me, actually, that there are so many physicians and scientists who balk at the idea of using old-fashioned remedies for disease processes. After all, digoxin is derived from foxglove, and its use to enhance cardiac function has been around since at least the 1800s. Granted, a lot of old-fashioned cures contain a lot of hokey-pokey-hocus-pocus, but you'd think that there'd be more interest in some of the more efficacious ones.
The one major flaw in many of the studies that have been done "disproving" the efficacy of herbs is that there is no standard for efficacy and no standard for the drug that's administered. That is, studies demonstrating efficacy (or inefficacy) in mice and rats use entirely different criteria from studies purporting efficacy (or inefficacy) in humans. Furthermore, animal studies tend to use various extracts of the plant, rather than the concoctions you can buy yourself in stores--and God only knows what sort of stuff ends up in those, since there are no standards.
I take St. John's Wort and licorice, myself--the St. John's Wort seems to help my longstanding depression, and the licorice seems to help my eczema (though that's probably also because it's summer). I take them as teas (one cup of each, once a day), and it really does seem to help--I hadn't noticed the effects of St. John's Wort, actually, until I realized that I was writing for hours on end, and that my concentration had improved. I was taking it almost daily, not because of any special effects, but simply because it tastes good (to me, my counterpart hates it). And then I realized that I felt much the way I did when I was on a prescription antidepressant. The licorice is more hit-or-miss, but either way, I take it, because sleeping at night, even if it is a placebo effect, is good.
For a long time, too, I've used lavender oil on my skin, ever since that time I bought, on a whim, a little tiny tub of lavender skin balm from Terralyn. I used it because it smelled good and kept my dry skin at bay--it wasn't until I gave it to my sister to try (her eczema is far worse than mine) that she told me that it was the first thing she'd used in over 3 weeks that worked.
So my own feeling about herbal medications is generally good. But then again, I also happen to be exquisitely sensitive to drugs. Three hits of pot will knock me out, a small glass of madeira puts me to sleep, and a little extra St. John's Wort hurtles me into orbit with anxiety.
Of course, the science says that I'm a lunatic for thinking that these work, since the evidence is mostly to the contrary. But I don't think science can deal with herbal medications the way it can with chemically-engineered drugs. You can't isolate one compound from a plant and expect it to work the way taking the whole plant (part) works. After all, licorice root contains something like twenty different compounds, of varying efficacy, but the sum of them (for me) is less itching at night. There may not be known receptors for these compounds, and there may not be known pathways by which they all work, and we may never know for certain how much of the effect is due to one compound or the other. But just because we don't know the hows or whys doesn't mean it's not real.
If you're interested in using herbs, it is my recommendation that you do your own research as to which ones are right for you. If you have high blood pressure, for instance, stay away from licorice, even if you do have eczema. If you're fond of cheese and red wine, St. John's Wort may not be right for you. And so on--there are as many considerations for which herbs to take as there are for drugs. Keep in mind, these are drugs, and just because they are natural does not mean they are safe. Herbs for Health and Healing by Kathi Keville is a good place to start with your own research. It's not the end-all be-all to everything herbal, and it's coverage is almost exclusively from a Western perspective, but as a beginner's guide, it can't be beat.