Ok, I've got a puzzle for you all as my first post on the site!

We've been growing herbs in our front yard in three raised beds for a few years, though have been fairly lazy about it. however, I'm not asking about weed problems - we know we're bad about keeping up with that. The puzzling problem came last night when we went out to grab some of the oregano for some pasta sauce, the first use of the season.

The oregano tasted strongly of oregano like it should... and was as spicy as a habanero! Ok, not quite, but way spicier than a jalapeno, AND it left a numb feeling for several minutes that I don't normally experience even with hot peppers directly. It wasn't really pleasant (especially that numbness) and was actually far too spicy for some of the family members for us to dare putting it in the sauce for the oregano flavor.

Now, we had at one point planted a few capsicum plants in that bed as well, but had never really had much success with them. A few good peppers, sure, but only so-so in quality/size/flavor. We hardly pay any attention to them anymore.

We have a couple of theories, but not sure of the logic of them:
1) Soil contamination from the pepper plants: capsaicin being leached into the soil from the pepper plants and then being absorbed by the herbs.
2) Accidental cross-breeding: if the long-ignored plants have spawned a terrifying pepper-oregano hybrid we should burn and run away from before it rises up to kill its masters.
3) Chemical contamination: the beds are only about 6ft from the road. Far enough that the snow banks don't press into them in the odd New England winters. However, it's close enough that perhaps something could have gotten intentionally or unintentionally sprayed that far and contaminated the soil or the surfaces. There's no obvious chemical taste/smell/feel, but I suppose it's still something to consider.

Anyone have an idea as to 1) why this happened or 2) how we can undo it?

Thank you!
~Warren Huber