The histamine model for CFS may apply to some. I know two people that had CFS which ?progressed? to histamine intolerance. With the gut model for CFS, a percentage could go down that pathway. My thinking is that a percentage of histamine intolerance patients is caused by overgrowth in the gut some histamine producing species, thus reducing them should reduce symptoms.
Tonight I decided to gather up as much information about known histamine producing species as a start point. A 1991 study found just 55 of 568 examined bacteria produced histamines (about 10%) and of these 55, 51 were Enterobacteriaceae.
- Proteus morganii, All species. This is a species that is normally in the gut, thus it’s overgrowth is reasonable.
- Klebsiella pneumoniae, 5/6 of the species
- Escherichia coli, just 1/3 of the species
- Enterobacter aerogenes,
- Enterobacter cloacae ,
- Proteus sp., (vulgaris, mirabilis.
- Edwardsiella sp. ,
- Vibrio spp.
- Source: [ref] 
The Proteus species were more active at a pH of 5(acid) than pH 7 (Neutral), which may account for severe reaction to lemon and grapefruit juices because they will grow much better in that environment. It also hints that using baking soda (high pH) may reduce the histamine production.
Fish: Many species have high or even extreme level of histamines, these include: saury, tuna, bonito, butterfly kingfish, mackerel and mahi mahi.
What are the convention symptions of histamine excess?
“Onset of the poisoning symptoms ranges from a few minutes to a few hours after eating. Victims generally experience a flushing of the face and neck, a throbbing headache, dizziness, faintness, and an itching, burning sensation in the
mouth and throat. The fish, as consumed, may have a sharp, peppery flavor and invariably contain high levels of free histamine, usually in excess of 100 mg/100 g”. Fresh tuna have been reported to be often at 600 mg/100 g.
Treatment of Morganii
According to Wikipedia, the following have a high success rate, but more and more resistance is reported.
- Third-generation and fourth-generation cephalosporins
In terms of herbs, Salvia officinalis (common sage) has a 75% inhibitory rate[2004 Full Text] (versus 90% with the above antibiotics). Clove Oil, lemongrass and sweet basil oils are also reported effective (listed in order of effectiveness). Another study found Cinnamon and clove did better(significant effect) than turmeric and cardamon(moderate effect) 
So we do have a set of easy to obtain spices and herbs that would inhibit Morganii (assuming that the histamine issue was cause by an overgrowth of them).