There is an interesting post by Dr. Tania Dempsey which discusses why there are a great number of false negatives with urine testing. https://www.drtaniadempsey.com/single-post/Ask-The-Expert-Mast-Cell-Activation-Syndrome . Here is an excerpt: many mast cell mediators have very short half-lives and quickly break down when exposed to heat (certainly body heat, and perhaps even room temperature heat). For example, prostaglandin D2 and heparin — both mediators relatively specific to the mast cell — have very short half-lives, on the order of about one minute. Therefore, if the blood or urine specimen in which we intend to measure levels of these mediators is left exposed to heat (even room temperature) for one minute after collection from the patient, one-half of the prostaglandin D2 and heparin in that sample is now gone, leaving one-half of what was originally there. And if the specimen is left unchilled for a second minute, then one-half of the remaining one-half is now gone, leaving only a quarter of what was originally there. You can see how a specimen for prostaglandin D2 or heparin testing doesn’t have to be left unchilled for very long before most of what you’re looking for has disappeared —

Hi Mary,
I think infections including SIBO can provide the ‘perfect storm’ and contribute to onset of mast cell symptoms. It can be a very transient problem for some–and others more chronic….from my experience. Good to hear from you!

Thanks for stopping by my blog, Tara!

Jeanne, in clinic I do see some overlap with mast cell issues and sibo. Not sure if it is a cause or effect.

You are most welcome, Pat. And, no, it’s not in your head. These disorders are difficult to tease out!