Reminder: Probiotic can cause major herx!

“Hi Ken,

Here’s some more grist for the CFS Remission mill. I had been much improved by upping my Vitamin D and adding Symbioflor-2. I was even working 20+ hours a week, a huge amount for me over the last five plus years. On top of those two mainstays, I rotate in another probiotic. Since I’m always low in Lactos and Bifidos via many stool tests over the years, three of which are featured on your blog, I aim for your recommendations on those. I’m no longer usually that sensitive to most supplements and probiotics and usually react well to Bifidos, especially for a slight but very elusive change in brain fog. But last Friday night I took ONE of these puppies and have been suffering ever since. The next day I could barely move and had to resort to pain killers, the histamine reaction is still going strong with blocked sinuses and runny nose and constant sneezing. Here is a link to the Bifido only probiotic I took, which I believe is mentioned on one of your posts. There are several versions of this 25 Billion Bifido only option from Renew Life, but they seem to contain the same ingredients.
Forgot to mention that I used some of the techniques you mentioned on your blog, I think from a post about a friend having a tough reaction to a probiotic. I’m bombarding myself with probiotics I know I can tolerate as well as antihistamines (OTC, quercetin, turmeric, anything I have on hand) and that has helped. Without your blog, I wouldn’t have even know that a probiotic can cause such a herx or histamine response and probably would’ve just kept taking it and chalked it up to a “flare” or bad seasonal allergies.”

On a related note, a reader asked about which version of Reg’Active (L. Fermentum ME3)

The answer is simple, start with the lower dosage one.  Some readers have reported major herx from this probiotic. If you have capsule making equipment, consider splitting the capsules into smaller dosages.

Back to the above issue. The herx/histamine causing bacteria consisted of:


First, remember that doing single species probiotics is the safest path when practical (ideally with the strain named — above lack any strain information 😦 )

Second, search pubmed, it is not hard, just enter the words!


  • “Human peripheral-blood-derived mast cells were stimulated with Lactobacillus rhamnosus (L. rhamnosus) GG (LGG(®)), L. rhamnosus Lc705 (Lc705), Propionibacterium freudenreichii ssp. shermanii JS (PJS) and Bifidobacterium animalis ssp. lactis Bb12 (Bb12)” [2011] mast cell stimulation releases histamine.
  • Bifidobacterium bifidum G9-1… whereas those in mast cell mediators, histamine and cysteinyl leukotrienes were not [suppressed].” [2015]
  • Bifidobacterium infantis and Bifidobacterium longum… Prolonged treatment …significantly suppressed both the allergy-like behaviors and all of the above mentioned factors involved in histamine signaling.” [2008]

In other related articles, bifidobacterium reduced allergies over 2-4 months.  It appears that this may be due to this bacteria displacing higher histamine producing  bacteria over time. It does not mean that these probiotics do not produce histamine.

Bottom Line

Go slow and gentle with probiotics.  Antibiotics, herbs and spices flow thru the body with a drop of 50% (half-life) in a few hours usually.  Probiotics are living creatures that may not drop, but increase!! When you have too severe a probiotic herx, it can become a challenge to moderate it. A high dosage of probiotics that you do well with, may help — you are trying to displace the herxing probiotics.

In some cases, there are other probiotics known to be hostile. For example, lactobacillus and Clostridium butyricum (Miyarisan) will moderate E.Coli probiotics.

Start with low dosages and slowly work up — if you slip into a herx, it may last a much longer time than expected.