On a related note, a reader asked about which version of Reg’Active (L. Fermentum ME3)
Reg’Activ Detox & Liver Health, 60 Capsules – 6 billion CFU
Reg’Activ Immune & Vitality Capsules, 60 Count – 4 billion CFU
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)”  mast cell stimulation releases histamine.
- “Bifidobacterium bifidum G9-1… whereas those in mast cell mediators, histamine and cysteinyl leukotrienes were not [suppressed].” 
- “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.” 
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.
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.