If you get problems when you take an herb then you're using the wrong herb.
People love to blame even severely debilitating problems from some new herbal blend they take on a "healing crisis".
I've seen a lot of clients since I started to work as a herbalist in 1998.
The only time I've ever seen a healing crisis was in a client who came to see me with 10-year old chronic giardiasis. About 5 weeks into his herbal formula he got a very high fever for three days, after which the giardia was gone (we think. If it comes back he'll call me again.).
But to get a healing crisis when you take herbs that should strengthen you, shore you up, help you cope with life? Never.
Smart clients stop taking their herbs if they get worse from them, and call up the herbalist: "this gives me such-and-such trouble, should I continue?"
The smart herbalist says "No way! Those herbs are obviously wrong/too strong for you, I'll give you a different formula".
It's rare that clients get problems from a formula I've given them, but still, it can happen. Which is why I tell my clients that they should call me if they get undesired reactions.
Because if they do, they have the wrong formula.
Healing crisis, my tiny hiney.