CAUTIONS for Tart cherry (Note; This isn't a complete list) Cherry is considered to be a toxin at high doses, and it also interferes at least somewhat with P450 cytochrome, the main metabolic pathway that involves metabolism of herbs or drugs. WebMd says this is a mere moderate caution however.  I've had no trouble with either, but I certainly take it in lower levels just on my legs and I've had no trouble here. (Note that as sites like Aromatherapy World say, dermal use of herbs often reduces toxicity relative to value 100's of times.) You can also take cabbage or brocolli powder cheap online at Amazon, etc. Cabbage improves P450., Tart Cherry is also a poison if used for long term use; Just a few days at a time to then let it cleanse out of my system; On other days for DOMS (muscle soreness) I take axtaxanthin, MSM, and or flax oil.These involve removing hydrogen ions that have been found to be the real cause of DOMS (not lactic acid buildup). One type of toxicity to watch for is lower back discomfort, it toxifies renal function. WebMd says it's likely safe, even so Tart Cherry is also highly allergenic, so take with considerable caution. I've had no problem here either, even so no doubt proceed with caution.  It's also the strongest anti inflammatory food known. This may be important for CFS since inflammations are common. It's great for e.g. dental issues, itching, otitis, sinusitis, and so on if used at the lower dose than recommended by DR. Fizz Hd on the bottle. It's also the strongest antibacterial I've seen in 13 years of search. Tart Cherry relieves my exercise edginess dramatically because it not only stops the DOMS, it also boosts melatonin a soothing natural compound found in all cells in the body, but unlike melatonin it doesn't cause drowsiness.(This is only after you either perhaps "cure" your CFS or control it with U.D.G. or Activive as I say on the post below. Without being in the general area, I would think Tart Cherry or axtaxanthin etc. wouldn't help much since most herbs won't make a dent in your CFS, including the cherry. It boosts these methods, but it may not be the best without them.).