I've honestly had some doubts about Ehrlich's reagent (at least on its own) for a while now. Sure It's better to test drugs than not, but indole molecules are pretty common and easy to find. I'm not sure how viable it would be, but one could add some tryptophan or 5-HTP while laying RCs to get false Ehrlich's positives.
Similarly, fungi and plants can (and do) produce serotonin and other indole compounds that would also react w/ Ehrlich's, thus giving a positive result.
I'd love to see if our more chemistry inclined folk (@Phineas_Carmichael or @Norman) have any light to shed on my suspicions, and could perhaps assuage them.
Edited by HrVanker, 13 December 2021 - 02:35 PM.