This post examines four conditions that can be co-morbid, which fits the microbiome model. The differences may be a combination microbiome strains and DNA SNPs. I have already posted about SNPs associated with MCS in this page (which I just updated).
- MCS – Multiple Chemcial Sensitivity
- EHS – electro-hypersensitivity
- IEI – idiopathic environmental intolerances
MDAS – multiple-drug allergy syndrome
- hyper sensitivity to drugs is common with CFS/IBS/FM
NS – noise-hypersensitivity (hyperacusis) – prevalence ~ 3.7% in general population 
- Associated to Lyme 
“Diagnosis of MCS can be difficult because of the inability to assess the causal relationship between exposure and symptoms. No standardized objective measures for the identification of MCS and no precise definition of this disorder have been established.” 
- MCS affects middle-aged women with comorbidities (chronic pain, fibromyalgia and chronic fatigue)
- “relation between noise and odor sensitivity reflects a general environmental sensitivity.” 
- “The estimated prevalence of MCS was higher among allergic patients than non-allergic participants. People with experience of dwelling in a new house and atopic dermatitis were more at risk of being intolerant to chemicals” 
- “Chemical Sensitivity Factor was associated with allergies and alcohol use.” 
- “Much of the controversy over the causes of electro-hypersensitivity (EHS) and multiple chemical sensitivity (MCS) lies in the absence of both recognized clinical criteria and objective biomarkers for widely accepted diagnosis…” 
- “Near 40% had a increase in histaminemia (especially when both conditions were present),”
- “. Both disorders were associated with hypoperfusion in the capsulothalamic area, suggesting that the inflammatory process involve the limbic system and the thalamus. Our data strongly suggest that EHS and MCS can be objectively characterized and routinely diagnosed by commercially available simple tests”
- ” Positron emission tomography activation studies with several different odorants showed in patients with odor-associated symptoms an odorant-related increase in activation of the anterior cingulate cortex and cuneus-precuneus in comparison with a control group.” 
- “confirming MCS altered (P < 0.05-0.0001) glutathione-(GSH), GSH-peroxidase/S-transferase, and catalase erythrocyte activities.. Severe depletion of erythrocyte membrane polyunsaturated fatty acids with increased ω 6/ ω 3 ratio was confirmed in MCS, but not in EHS…. identified significantly altered distribution-versus-control of the CYP2C19∗1/∗2 SNP variants in EHS, ”  – i..e. this has a DNA component
- ” high chemical sensitive individuals diagnosed by using Japanese criteria as MCS patients were more significantly associated with SOD2 polymorphisms.” 
- ” Interestingly, the NOS3 -786TT genotype was associated with increased nitrite/nitrate levels only in IEI patients… the (CCTTT)16 allele discriminates MCS..Here, we first demonstrate that NOS3 -786T>C variant affects nitrite/nitrate levels in IEI patients and that screening for NOS2A -2.5 kb (CCTTT) n polymorphism may be useful for differential diagnosis of various IEI. “
- ” We identified 183 substances whose levels were beyond the normal detection limit. The most prominent differences included significant increases in the levels of both hexanoic acid and pelargonic acid, and also a significant decrease in the level of acetylcarnitine in patients with MCS.” 
- “suggest that acetyl L-carnitine 1500 mg/day (500 mg t.i.d.) is also efficacious in improving depressive symptoms, pain, and the quality of life of FMS patients.” 
- ” these results indicate that LAC may be of benefit in patients with FMS, providing improvement in pain as well as the general and mental health of these patients.” 
- “. Our data show that administering ALC may reduce both physical and mental fatigue in elderly and improves both the cognitive status and physical functions.” 
- ” Preliminary evidence of a relation between post-infectious fatigue and mitochondrial dysfunction indicates a complex response involving acetylcarnitine”
- “Significant differences in plasma acetylcarnitine [41,42] were reported in CFS, while others found no difference [43,44]. There are several explanations for this discrepancy. One explanation could be that the selection of CFS patients differed. The patients of Kuratsune et al. [41,42] were selected according to the CDC criteria, but Jones et al  used the Oxford and CDC criteria.” — bacteria determines symptoms, symptoms determine selection. 
- “Of the 99 [CFS] patients investigated, 58 reported a decrease in the symptoms by the use of azithromycin. These responding patients had lower levels of plasma acetylcarnitine.” 
- “Plasma levels of substance P, vasoactive intestinal peptide and nerve growth factor, but not histamine, were elevated in patients with self-reported multiple chemical sensitivity (sMCS). Exposure to volatile organic compounds (VOC) increased plasma levels of all parameters in these patients, while it had no effect in normal subjects or patients with atopic eczema/dermatitis syndrome (AEDS).” 
- ” The phenomenon of electromagnetic hypersensitivity in the form of dermatological disease is associated with mastocytosis. The biopsies taken from skin lesions of patients with EHS indicated on infiltration of the skin layers of the epidermis with mastocytes and their degranulation, as well as on release anaphylactic reaction mediators such as histamine, chymase and tryptase.” 
- “Our data show an increased prevalence of metal allergy and elevation of mercury levels in bio-indicators among patients with MCS.” 
- ” the histamine-releasing activity of plasma from patients with MDAS was significantly increased and correlated with [Hyper coagulation] F(1+ 2) levels (r = 0.68; P = .04).” 
Some of the studies suggest (speculate) that the section of the brain that is over activated in a MCS/EHS reaction has become “hard-wired” to over react. This smells of “it’s all in your head and not real” view. Other areas of the brain alteration have been associated with microbiome shifts, so the hard wired aspect or psychological aspect is not probable.
My own experience is that I had mild MCS during one episode which disappeared afterwards. Not 100% disappear, I do notice some reaction to various chemicals in sufficient concentration — but I then remove myself quickly, and the reaction disappear quickly. From this experience, I infer that MCS/EHS may have a significant microbiome dimension. I prefer this view, because it gives hope for treatment and improvement.
I personally deal with two individuals that have MCS and hyperacusis; they also have severe problems with histamine. One of them had a full coagulation panel done just before a bad MCS exposure. Two weeks after the exposure, a second panel was done on this person and the indicator for active coagulation jumped extremely high (i.e. 6 Standard Deviation higher than it was before). Both went through the antibiotic rotations of Jadin without any change of THIS symptoms. Hence, those antibiotics are not good candidates for treating MCS.
“Immediately after taking 2-3 bites of cooked salmon, a clerical worker developed oral burning, urticaria, and asthma. In the emergency department, she was diagnosed with “allergies”; scombrotoxinism was never considered. She then developed wide-ranging symptoms (e.g., chronic fatigue, asthma, anxiety, multiple chemical sensitivity, and paresthesiae) and saw many specialists (in pulmonology, otorhinolaryngology, allergy, toxicology, neurology, psychology, and immunology). During the next 500+ days, she had extensive testing (allergy screens, brain MRI, electroencephalogram, electromyogram, nerve conduction velocity, heavy metal screen, and blood chemistry) with essentially normal results. She filed a workers’ compensation claim since this injury occurred following a business meal. She was evaluated by a Qualified Medical Evaluator (GL) on day 504, who diagnosed scombrotoxinism.”  [Full Text]
Normally, “Symptoms typically occur within 10–30 minutes of ingesting the fish and generally are self-limited. …. However, symptoms may show over two hours after consumption of a spoiled dish. They usually last for about 10 to 14 hours, and rarely exceed one to two days.”[Wikipedia] In this case, it persisted for over 500 days… with antihistamines being ineffectual. Morganella morganii is one bacteria that is associated with this condition. ” some M. morganii strains are resistant to penicillin, ampicillin/sublactam, oxacillin, first-generation and second-generation cephalosporins, macrolides, lincosamides, fosfomycin, colistin, and polymyxin B” [Wikipedia]
“Others, especially the Enterobacteriaceae, are contaminants that are introduced post-harvest. It is this second group that is considered most important in the development of histamine.” [Food Safety Watch] Enterobacteriaceae are one family of bacteria that are reported as major overgrowth in CFS.
If you have low acetylcarnitine, then the antibiotic azithromycin (a macrolide) and acetyl L-carnitine 1500 mg/day (500 mg t.i.d.) may help. Rotation to different macrolides see macrolide page for a list of them), with Telithromycin and Solithromycin being interesting because they are not widely used (and thus more unlikely to be resistant).
Enterobacteriaceae and M. morganii are suspects. With the high degree of antibiotic resistance, the benefits of doing rounds of (different) antibiotic resistance is questionable. There were no published studies on antibiotics and MCS that I could locate. I could not find any studies using fecal transplants for MCS or EHS — positive results of such studies would likely confirm a microbiome aspect.
All of these conditions appear to be connected to excessive release of histamine into the body and possibly link back to Enterobacteriaceae overgrowth . This could be normal release coupled with an excessive background level of histamine due to overgrowth of some bacteria, or a mis-signalling for histamine release. Often the body has a Ying/Yang aspect. The signal to release is combined with a signal to constraint. If the signal to constrain is inhibited, excessive histamine may be released.
Hexanoic acid and pelargonic acid being high may lead to identification of the bacteria because these chemicals tend to be used as antibacterials against many species. This hints that the bacteria(s) causing this condition produces them against other bacteria.
- “some natural microorganisms have been screened and evolved to produce hexanoic acid,” 
A reader wrote that after a bad MCS exposure,
she took a full dosage of Mutaflor and Symbioflor-2. She slept hard and almost all of the symptoms were gone afterwards.