You can follow my experiments in the thread Possible PEM Blocker in this sub-forum. I don't have a theory for why it works. It's just something I observed by chance, and verified its effect by experimenting.
Cumin isn't hot, and while I don't really care for the taste, I don't find it unpleasant. I just take a level tsp of ground cumin (no-name store stuff). I hold it under my tongue for a few minutes, since I think it works on the brain, and taking things sublingually is more efficient at getting the chemical to where it does the most good (and least bad if there is any). For me, it blocks exercise-induced PEM 100% for about three days. It starts reducing existing PEM symptoms after 2-3 hrs.
Cinnamon and turmeric, along with several other spices that are antioxidants or peroxynitrite scavengers, make my symptoms dramatically worse, so I have to avoid them. Cooking doesn't seem to affect cumin's effectiveness.
Perilla is also rich in cuminaldehyde, so it might work as well. I haven't had a chance to try it yet. Maybe I'll order some seeds this year. It says to plant after temperatures are reliably over 8C, so that's not happening soon (a few years ago I had frost June, July, and August). If cuminaldehyde works for you, but you detest the taste, you can give perilla a try.