For example, Foxglove is a very poisonous plant - beautiful, but poisonous. It has been used for many years, in the form of digitalis, to correct some heart rhythm problems. However, digitalis has a VERY narrow range of safe dosing, and isn't appropriate for all people with heart problems.
It makes me very nervous when I over hear people talking about how excited they are that they're treating themselves with "such and such" herb, without their doctor's consent, without discussing their use with any herbal professional and often without telling any of their health care providers that they are using said substance.
Some herbs have interactions with medications and these interactions can be very dangerous. Some medications may have their effects negated. Some medications may have their effects multiplied. In both cases, imagine the consequences being equivalent to not taking the medication or taking more than the prescribed amount. The results could be catastrophic for some patients!
Some herbs are not meant for all presentations of a symptom. For example: ginger. Read my personal story of Why you have to be careful with home herbal remedies, and you'll see how the side effects can be very uncomfortable and avoidable. I was lucky that I eventually recognized the problem, but what if you weren't aware of the possible side effects? You might suffer needlessly! Some people are even prescribed medications to counteract such side effects. This is so unnecessary!
It's great to use natural products, because the chance of side effects, when used properly and under knowledgeable supervision, is greatly reduced when compared to biomedicines. However, natural substances should be considered as medications, something that is prescribed with assistance from a trained professional.
Feel free to talk with your acupuncturist about any natural substances that you are taking or are considering taking. At least, you may save yourself some unnecessary side effects, at most you may save your life.