Thanks Lotte,
Comfrey is an amazing herb and great that you have used it and can find places to buy it. In the Dutch stores that still sell the root to the general public, they are supposed to give you a paper to explain that it should not be used internally. So lo ng as the use is really short term, and if the person has no liver disorder, this is likely very fine. So short term if internally (though not officially in Europe) and external use should be perfectly fine – and very helpful.
Foraging, Growing and Using Herbs in Cities