Recently a question was asked about the possible substitutes that could be used in place of the Chinese herb “xi xin” (細辛) Asarum sp. because the practitioner was concerned the this herb is “toxic.” This post is part of my response and a very short over-view of the literature on this herb in regards to its toxicity and dosage. This is not meant to be exhaustive in any way.
|Asarum delavayi 川滇細辛 Yunnan, China|
While I will agree that xi xin has some minor toxicity issues, I also think it is quite safe when use appropriately. I guess when I hear a practitioner say they don’t want to use an herb because it is toxic I feel the need to try to tease out where this is coming from in hopes to better understand how practitioners are thinking. Also, when one says they don’t want to use an herb because it is toxic, I start to wonder what “toxic” means to that person. If you take enough of anything it can be toxic.
I took three random books on materia medica in Chinese off my self and found this information. The first one is “Clinical Uses of Chinese Medicinals” which states xi xin “has small toxin” or it may be translated “slightly toxic.” Of course when a Chinese book says that there is no way to know if they are referring to toxicity as we might think of it, i.e. there is some chemical in the substance that may cause cancer, or it it is just really “hot” and when used in large doses can cause noticeable physical “side effects.” The other two are transcibed lectures from very well known materia medica scholars Lectures in Clinical Uses Chinese Medicinals by Zhang Ting-mo and Lectures in Chinese Medicinals by Yan Zheng-hua. Interestingly neither mention toxicity of xi xin and combined the two take up nearly 6 pages of writing. That’s a lot of talking about an herb without any mention that it is toxic, don’t you think?
The Grand Dictionary of Chinese Herbs lists 16 species (plus a couple sub-species).
Asarum debile (tong qian xi xin) no mention of toxicity, dosage 2-6g
Asarum caudigerum (wei hua xi xin) has small toxin, dosage 3-6g
Asarum caulescens (shuang ye xi xin), A. himalaicum (dan ye xi xin), A. chinense (chuan bei xi xin), A. fukienense (fu jian xi xin), A. delavayi (chuan dian xi xin) are all under the heading of “tu xi xin” there are several different sources cited for these herbs. One says there is no toxicity while another cites some research that suggests over-dose could cause difficulty breathing. I don’t have the research, so I don’t know any more than that. Dosage 1-3g
Asarum forbesii (du heng), A. ichangense (xiao ye ma ti xiang) have entries for both non-toxic and “has small toxin” dosage 1.5-6g
Asarum geophilum (da kui wa) listed as non-toxic, dosage 1-3g
Asarum heterotropoides (bei xi xin), A. sieboldii (hua xi xin), A. sieboldii var. seoulense (han cheng xi xin) all under the heading of “xi xin” and is said to “have small toxin” although a number of the older texts cited such as the Shen Nong Ben Cao and the Bie Lu either don’t mention toxicity or say it is non-toxic. Dosage 1.5-9g (1-3g when used as a powder)
Asarum splendens (hua lian xi xin) “has small toxin” dosage 2-3g
For fun, I also looked in the PMPH “jiao cai,” which is a pretty standard textbook and it says, 唯有小毒, 用当宜慎 “wei you xiao du, yong dang yi shen” which literally translates to “only has small toxin, use should appropriate caution” The second part of which I would render as “it should be used appropriately and with caution.” they give the dosage at 3-5g
I have harvested 3 different species of this plant in the US, and used both these species and an unknown number of Chinese species for 20 years and never been concerned with their toxicity. I use it appropriately, simple as that. This herb has a pretty narrow usage and is extremely effective when employed properly.
|Asarum marmoratum with flower inset bottom right corner. Photo from Northern California.|
So, I would say that anyone who has graduated from a reputable school, having studied Chinese herbs (or Western herbs for that matter) should be able to very comfortably employ any Asarum species without being concerned with toxicity. I am not saying one should not be aware of its restrictions, but being aware of, say dosage, should be pretty basic and, rightly or wrongly, I assume that a licensed practitioner should know this information about any herb they use.