In my last post, a reader cites taking caprylic acid or octanoic acid which I have not covered yet in any post.
- “Taken together, these results indicate that combined treatment with low concentrations of caprylic acid and citric acid, which are of biotic origin, can eliminate microorganisms from unpasteurized carrot juice.” 
- “The levels of medium-chain fatty acids (MCFAs: pentanoate, hexanoate, heptanoate, octanoate and nonanoate), and of some protein fermentation metabolites, were significantly decreased in patients with CD, UC and pouchitis.” 
- “the 4 fatty acids : caproic acid, caprylic acid, capric acid and lauric acid in vitro. All four inhibited not only the mycelial but also the yeast-form growth of Candida albicans. In particular, capric acid and caprylic acid inhibited Candida mycelia growth at very low concentrations.”
- “The data indicate that exposure to lauric acid (C12) was the most inhibitory to growth [of Clostridium difficile] (P<.001), as determined by a reduction in colony-forming units per milliliter. Capric acid (C10) and caprylic acid (C8) were inhibitory to growth, but to a lesser degree.” 
- Caprylic Acid reduces enteric campylobacter colonization in market-aged broiler chickens but does not appear to alter cecal microbial populations .
- “Results indicated that caprylic acid, monocaprylin, and sodium caprylate could potentially be used to treat Dermatophilus congolensis infections.” 
- Antibacterial effect of caprylic acid and monocaprylin on major bacterial mastitis pathogens .
Clear impact on Lactobacillus, Bifidobacteria and Enterococcus could not be found. It was effective in reducing bad E.Coli strains. There are no results for fibromyalgia, chronic fatigue syndrome or irritable bowel syndrome.
There is nothing that explicit said that you should not use it. On the other side, there is nothing that clearly says that you should use it (unless you have candida). It does not appear to alter the microbiome in any significant method.
Bottom Line: No opinion.