A reader asked me about silymarin AKA milk thistle, while I have made passing references to it, I have not done a drill down on PubMed, so it is time to do so. Search on PubMed found for milk thistle….
- and IBS: no articles
- and CFS: no articles
- and fibromyalgia: no articles
- and coagulation: no relevant articles
- and bacteria: 38 articles.
- ” Affecting the microenvironment of the gut, including SM-bacteria interactions, awaits future investigations.” 
- “Gram-positive bacteria were inhibited at concentrations between 60 and 120 μg/mL. Gram-negative bacteria were not inhibited by the silymarin concentrations included in this study.. . We demonstrated that silymarin shows antibacterial and antiadherent/antibiofilm activity against certain standard bacterial strains which may be beneficial when used as a dietary supplement or a drug”  – no significant effect, no information on whether the shift would be for the better or the worst.
- “The results showed that silybin inhibited RNA and protein synthesis on gram-positive bacteria.” 
- “Potentially toxigenic molds from the Aspergillus sections Flavi and Nigri as well as Eurotium, Penicillium, Fusarium and Alternaria species were isolated from Milk Thistle supplements (sold in the US). The predominant molds were Eurotia (E. repens, E. amstelodami and E. rubrum), A. flavus, A. tubingensis, A. niger and A. candidus. To our knowledge, this is the first study reporting on fungal contamination profiles of MT botanicals.” 
- “A total of 83 Milk Thistle samples from the US market were analysed. The aflatoxigenic fungus Aspergillus flavus were detected in 19% of the samples with levels ranging from 0.04 to 2.0 µg kg(-1).” 
No demonstrated benefit for CFS/IBS/FM patients have been reported. There is a 1 in 5 risk of toxigenic molds.
Impacts gram-positive bacteria at high dosages which may includes: Bacillus (in some probiotics), Clostridium (Miyarisan probiotic), Steptococcus (Enterococcus) and Straphylococcus. Other uses, per wikipedia, “Milk thistle has been used for a number of purposes including liver disease, and cancer; however, clinical studies are largely heterogeneous and contradictory”
I cannot put this on a recommended list – no demonstrated benefit, risks