You had initial good response from the niacin and/or the multivitamin with niacin. It makes some sense to me that taking a multi would be better since at least there is an attempt at balanced nutrients in the multi.
Lyme is a very complex disease to tackle, and literally anything can set off lyme patients. You need to be careful with each thing you try and not go past your limits.
what happened is so obviously not caused by anxiety since the anxiety happened AFTER your adverse reaction. Your first attempts did not cause this horrible reaction, therefore everything was fine at that point. Sometimes the illogical interpretations people present (pz) boggle me.
It's obviously an organic physical reaction going on, whether it's a strong herx/histamine induced toxin release, adverse niacin reaction, lyme herx, or other adverse reaction or chain reaction caused by the whole process. Of course you are going to be prone to some anxieties since you have a serious illness.
I would not pay attention to pz, he is just covering his ass because he wasn't aware that niacin can cause adverse reactions.
Every post of his makes me cringe now due to the lack of knowledge, sensitivity to who is responding to, and the bizarre accusations of not reading the text when it is he who does not read or comprehend what's going on.
I would have a look into Ray Peat's articles on pufa detoxifcation and niacin speeding this up. This could also be a factor in what happened to you. Lyme patients are often adrenal cases, so anything that affects histamine response will hit them hard. There are a LOT of variables at play always.
You could try to elminate all pufa from your diet for a few weeks or more to see if this helps, and replace with coconut or butter and small amounts of olive oils.
In general for lyme you should look at mineral status with a hair test, and look for hidden heavy metal toxicity.
You need to pay special attention to supporting the body and not just detoxifying.
Find out your optimal macronutrient sweet spot: Fats/Carbs/Protein.
I could write 300 pages more but I just don't have the time or energy to go into the detail necessary, sorry.
Newport might deign to help you out if you find him in other forums.
In my experience the b vitamins need to all work together in tandem, and I have seen more than a few times people having problems taking isolated B's. I usually recommend broad based food sourced B's from brewer's yeast or bee products or fermented foods.
As I said previously there are other and potentially better ways to go through the detoxification. I experimented with niacin many years ago and after the novelty of the flush wears off it's not really a great way to detox. you can sauna for the rest of your life safely and easily, and not get into any adverse reaction scenarios like this one, just let your body slowly get rid of what it sweats without forcing the issue. hyperthermia is also great to reset your basal temperature which will then cause a very effective detoxification of temperature sensitive pathogens. Often lyme people are hypo-metabolic. Hot/cold alternating showers pioneered in europe will achieve similar results - very safe unless you have severe heart condition.
Look into Stephen Buhner's herbal protocol.
The ionic foot baths are good too, but start slow.