> lost their sensitivity to poison oak via the accidental chronic exposure regimen
This is not how the immune system is known to work.
Sensitivity does not downregulate. Increased exposure enhances detection and response. Recognition proliferates. Once you're allergic to something, it'll only worsen.
You can become allergic to new things, but you won't lose allergies unless the recognizer population dies off entirely. And even if it did, you're likely close enough to training your immune system to this sensitivity again. (You've already done it at least once.)
This is not how the immune system is known to work.
Sensitivity does not downregulate. Increased exposure enhances detection and response. Recognition proliferates. Once you're allergic to something, it'll only worsen.
You can become allergic to new things, but you won't lose allergies unless the recognizer population dies off entirely. And even if it did, you're likely close enough to training your immune system to this sensitivity again. (You've already done it at least once.)
It's a failure mode of adaptive immunity.