Here's some information I pulled from this webpage:
http://www.alternative-healthzine.com/html/0203_1.html
Might be of use to you...
Comfrey
Comfrey root is not available for internal use in the UK, because it contains chemicals called 'PAs'. These caused liver problems for a very small number of people in Europe, so it was banned for internal use. However, the leaf does not contain these chemicals - so you can drink lots of Comfrey Tea with official agreement. You should do this if you want to encourage healing in the gut, or anywhere else; if you have arthritis or rheumatism; if you want to settle the stomach. Comfrey is a fantastic herb - if in doubt, use it! As with many garden herbs, there are a number of varieties. The one used medicinally is Symphytum officinale.
Chickweed
This 'weed' may be growing wild just outside your house; here is a good web page to aid identification -
www.ppws.vt.edu/scott/weed_id/steme.htm
Chickweed Tea is found to be good externally for many skin complaints. It will often reduce itching, and promote healing. It is often mentioned as helping weight loss - I am not sure of the mechanism here - but, again, if it replaces tea and coffee it's all to the good. It has a general benefit for the body, helping with rheumatism and arthritis.