I just learned from my MCAS doc that Ketotefin is available in an eye drop form called "Zatidor" in the U.S. (not sure about other countries) and it is non-prescription/ OTC. I've been having horrible reactions to smells since a flood in our apt that led to new walls, ceilings, carpet, paint, etc, and cannot tolerate them as hard as I try. My MCAS doc said that the memory of the smells get embedded in the nerves in us in a way that they do not in normal people. (Am paraphrasing and this is not a direct quote!) He said that these Ketotefin eye drops can also be used as a nose spray and can sometimes help with this issue. I found them at CVS today and tried them as an eye drop with no issue so will try it as a nose spray next. If it could help me to tolerate smells, it would be amazing and just wanted to post this in case it can help anyone else out there. I had no idea this product even existed! Has anyone else ever used it for MCAS or allergies? If it works well, I will replace my prescription eye drops which would save a lot of money!