I recently posted Stephen Buhner's response to that question:
"Stephen’s response:
If you are not currently sick, you can certainly take astragalus. The reason for not recommending it is that astragalus raises the parts of the immune system that are overactivated in chronic lyme. Those parts of the immune system are highly effective against lyme early on and help prevent or reduce the disease but if they are low to begin with and you are infected the infection can spread more easily. After awhile the immune system does ratchet up those parts to attack the lyme bacteria but by then the spirochete has altered itself and is no longer very affected by them, those parts of the immune system then begin to cause some of the lyme symptoms people have making the disease a kind of autoimmune problem. My book Healing Lyme goes into this in a great amount of detail."
**Members with chronic lyme have posted that they do take astragalus..and the autoimmune problem has't happened.
If you decide to try it, as PeteZa said above in her post - low and slow.
buhnerhealinglyme.com/herbs/astragalus-contraindicated/