This is not how it works with these plants. Prolonged, sustained exposure results in worse symptoms over time as your immune response increases in intensity. https://www.pbsnc.org/blogs/science/poison-ivy-and-its-pals-...
Given that I know dozens of people who demonstrably lost their sensitivity to poison oak via the accidental chronic exposure regimen I outlined above, at the very least it should raise a scientific question. It would be easier to dismiss if it was an isolated case or two. No one exposes themselves like that intentionally.
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.
If you can't lose allergies, why is exposure therapy a thing?
One is correct in that repeated exposure to an allergen can upregulate IgE production, especially in cases of severe allergies like bee stings or peanuts. This is due to the immune system's sensitization process, where each exposure can lead to more intense reactions, driven by the Th2-mediated immune response that promotes IgE production and allergic inflammation.
However, one is also correct that controlled exposure through allergen immunotherapy (SCIT or SLIT) can downregulate IgE and mitigate allergic responses. This therapy works by gradually introducing the allergen in controlled doses, which shifts the immune response from a Th2-dominated profile to a Th1-dominated or regulatory T cell (Treg) profile. This shift reduces IgE levels and increases the production of blocking antibodies like IgG4, leading to long-term desensitization and reduced allergic reactions.
In particular environmental allergens (pollens, dust mites, animal dander, molds), insect venoms (bee, wasp) may respond well to immunotherapy but we’ve had poor success or disproportionate risk attempting to mitigate food allergens (peanuts, tree nuts, and shellfish), certain medications, and latex .
That's not true. Desensitization therapy often works.
The trick is to introduce the allergens into the bloodstream, bypassing the skin.
I don't think that's correct. If it were, then allergy immunotherapy wouldn't work. Which... it does. Not perfectly, and not for everyone, but it does for many.
Maybe there's a bit of short term immunity from severe exposure. I've never tested that since the discomfort from an intense rash makes me avoid exposure like the plague for a few years.
East Asian countries have a long tradition of lacquerware, which is made with urushiol-containing saps. https://en.wikipedia.org/wiki/Lacquerware
In fact urushi is the Japanese word for lacquer, the plant is in the genus Toxicodendron.
Like most jobs until recently, making lacquerware was hereditary, and (clearly) the people making it were able to withstand sustained and direct exposure. It's possible that there is a genetic proclivity involved in ability to do the work, but just as clearly, there is hyposensitivity gained in exposure.
Let me back that up with a citation. https://pubmed.ncbi.nlm.nih.gov/1839723/
I know next to nothing about these topics but there are some wildly opposite claims in this thread. Truth has the tendency, despite being complex, to generqlly favor one direction.