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Comment by jandrewrogers | Hacker News Reader

You don't need to eat it. A well-known phenomenon in the US military is that some of the sites for Basic Training of new recruits have prodigious quantities of poison oak/ivy/sumac as the local flora. As consequence of the military training, you are rolling around in those plants daily. Initially, a large percentage of people have the usual reaction but it quickly disappears after a few weeks and it never happens again, providing apparent permanent immunity.

This is in contrast to the experience many kids have in the US of sporadic exposure and no immunity. Apparently intense sustained exposure is required.

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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-...

That can't possibly be true.

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/

Wasnt there some sort of natural selection centuries ago so that only folks tolerant to such chemistry actually performed the job?

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.

That link doesn't make a claim quite that strong. I also don't know anyone that has eaten it.

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.

> 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.)

It's a failure mode of adaptive immunity.

I've lost allergies to chocolate and soy.

If you can't lose allergies, why is exposure therapy a thing?

You're training a different kind of immune sensitivity. You're still inducing inflammation, and you're still allergic, you just see less IgE response.

Simply because you’re both right.

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 .

How do allergy shots work?

Looks like you are giving "Ackshually" technically correct points, when it's clear what others are trying to say. Please engage with what they are trying to convey instead of coming up with technical gotchas.

> You can become allergic to new things, but you won't lose allergies unless the recognizer population dies off entirely.

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 necessary. I've been doing allergy immunotherapy for the past few years, and it's all subcutaneous. Definitely not into the bloodstream.

> Sensitivity does not downregulate. Increased exposure enhances detection and response. Recognition proliferates. Once you're allergic to something, it'll only worsen.

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.

From personal experience, exposure does not lead to lasting immunity. Quite the opposite. I've had several intense exposure rashes that were debilitating, like not being able to walk properly for a week due to leg swelling. And I still get rashes from poison oak.

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.

As an Army vet, this sounds ridiculous. You don't roll around anywhere daily, let alone on poison oak/ivy/sumac. What's your source on this?

His butt. He sources a lot from there.

That's the exact opposite to what happens with DCC in chemical labs. DCC reacts with amino groups in proteins, same as urushiol in poison {oak,ivy,sumac} and is a notorious sensitizer. It happens to some graduate students that they are unable to work in a lab any longer.

n=1 but I used to be immune to it, then one summer started landscaping, and probably weed whacked and pulled more of it than ever. Started with small hives, then small rashes. Then each successive exposure got worse and worse and I had to take a long course of steroids to stop a multi week outbreak. Still have scars 20 years later. For me, more exposure made it far worse.

About a half dozen times or more being exposed led to worse and worse reactions. It was awful.

I’ve also never heard from others that your body gets used to it. I’ve always heard it gets worse every time, which was my experience. Obviously anecdata.

Yeah anytime I've gotten poison oak, it spreads and just will not go away without antihistamines - I doubt I could ever grow tolerant to it.

My personal experience is quite the opposite. Repeated exposure to poison ivy resulted in worse symptoms each time, leading to a scar from one particular welt that lasted years.

Something similar happened to my father (we had moved to a new house that had a large patch that kept coming back) and the year before he finally managed to get rid of it, his reaction was so bad he actually couldn't eat cashews for a long time, since they can have traces of the urishol.

I doubt your claim but wanted to mention a La Honda local once gave me a ride stranded with a flat tire on Pescadero Creek Rd.

His pickup bed was full of poison oak and landscaping tools, arms and hands filthy from the work.

He warned me not to touch anything and not shake his hand etc. saying he's covered in poison oak but immune from the frequent exposure.

It's everywhere around here and I react horribly to it, but this experience lends some credence to your claims...

I would be very surprised if that works.

The component that causes the reaction is not the allergen. It's a chemical that reacts with multiple proteins in the body - it's a very reactive molecule and not at all selective.

So theoretically, subsequent exposures would create new antigens each time - molecules your immune system hasn't seen before.

Grandfather was in the military in WW2 and said he became immune to it around then. He used to pickup poison ivy and tell us "don't do this" while rubbing it all over his arm.

I'm not actually sure what the lesson he was trying to teach their was but in hindsight it's a cool flex lol

This is an interesting story. It definitely contradicts both current medical findings and anecdotal evidence that repeated exposures and repeated reactions generally worsen allergy to poison oak (and insect bites/stings, and other things). But there is a lot that is unknown about the immune system and it's not impossible that there could be other unknown factors that when combined with exposure could induce tolerance.

What does the military do for treatment of the rashes?

This reads like getting shot with ever increasing caliber of bullets helps build immunity.

My wife is allergic to a plant we have in the garden, 5 years of rashes and it’s not getting better.

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