Most of the herbal things I use are basically nutritional supplements. I consider them part of my diet. Most doctors, when prescribing, don't ask you about what you eat. So what do they care if I get my iron from red meat or from stinging nettle tea?
I am very hesitant to take anything that is meant to actually DO something. I mean the kinds of things that are referred to as "magic bullets" or "bandaids". I don't think a headache is caused by a deficiency of either willow bark or aspirin in my diet, so why would I fix it by eating one of those?
If there is an underlying cause of something, using a measure to interfere with the symptoms just masks it, letting it worsen without you knowing it is still there. Some alternative medicine practicioners are of the philosophy that when you treat a symptoms, it moves inwards. When you treat the cause, the symptoms move from inside to out and then disappear. So, by putting a cream on a rash, you could be driving that rash inside to one of your organs, where it can do a lot of damage before you know anything is still wrong.
