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> Which finally gets to my point: What are the allergic affects of the tree, its raw sap, the liquid lacquer, and maybe for hypersenstive/reactive urushiol allergies, the finished lacquer?

The Wood Database can be a useful practical site for this sort of thing. I found [0], a page for a different wood which is said to contain the same allergen:

> The sap contains urushiol (the same allergen found in Poison Ivy), and can still be irritating to some sensitized individuals even after the wood has been dried, and sap can also seep through some wood finishes to the surface of the wood.

Same as poison ivy? Count me out if true: I react badly.

[0] https://www.wood-database.com/rengas/

The Wood Database? Thank you for once again reminding me how incredible the Information Highway once was, and could be.

I lament our detour onto the Commercial Highway.

It's still out there! It only _seems_ distant.

> What are the allergic affects of the tree, its raw sap, the liquid lacquer, and maybe for hypersenstive/reactive urushiol allergies, the finished lacquer?

Essentially the same as for any other urushiol.

I'm highly sensitive and had to ask my partner not to get into kintsugi with the traditional lacquers because even the tiniest spot of urushiol and I will be considering a trip to the burn unit.

I've gotten a very mild reaction from ~century old lacquerware but I wouldn't expect that to be common, once it's fully cured. And just because it's mild doesn't mean it's any less itchy, trust me.

see https://news.ycombinator.com/item?id=46268130

> What are the allergic affects of the tree, its raw sap, the liquid lacquer, and maybe for hypersenstive/reactive urushiol allergies, the finished lacquer?

Answering my own question, based on reading my own source more carefully (Gladman 2006 p.122):

The Japanese urushi tree, T. verniciflua, is among "plants containing uroshiol cross-reacting chemicals", which are described as follows (note that genus Toxicodendron is in family Anacardiaceae):

"Similar compounds found in other members of the Anacardiaceae family, as well as in several non-Anacardiaceae plants, can lead to cross-reactions and to an identical clinical picture (Table 2). However, dermatitis induced by these cross-reactors is rare compared with the frequency of dermatitis from Toxicodendron species. The allergens in the non-Toxicodendron plants listed in Table 2 are generally noncatechol phenols and resorcinols, and not the highly allergenic catechols in poison ivy, oak, and sumac. The hypothesis that early skin exposure to catechols may allow cross-reaction to other Anacardiaceae, whereas early oral exposure to phenols and resorcinols may induce tolerance, has been expressed."

Regarding the chemical composition, urushiol (in poison ivy/oak/sumac): "is a mixture of 3-n-pentadecylcatechols, which contain a catechol ring moiety substituted with different aliphatic side chains at position 3 or 4."

Some people react very badly, some are immune. But to be honest I just don't like my spoons and cups to look lacquered and I don't prefer the process of application.

Nothing wrong with that though, I like reading and watching people do the process and seeing them enjoy the calmness in doing dozens of layers over multiple days. Some end up with very beautiful shimmery brown wooden pieces [0] and I would love to own some of them. It's just not my style.

[0] https://www.youtube.com/shorts/j1YHhsHZOGk

If you're interested in Urushi, here's an account from an artist who went to Japan to learn how to work with it - https://garlandmag.com/lacquer-god/

"Essentially a concentrated form of poison ivy, uncured lacquer causes blistering rashes which cause its sufferer almost unbearable itch and many sleepless nights. Building tolerance typically takes up to two years and has students living in constant fear of the very material they eventually hope to use on a daily basis."

Ouch. Rereading my source above (Gladman 2006), they say hyposensitization (desensitization, if I understand correctly) generally doesn't work, but ...

"Lasting natural hyposensitization has been reported, however, among Japanese woodworkers who use lacquer derived from Toxicodendron verniciflua, the Japanese lacquer tree. In a 1991 survey, 81% of craftsmen developed dermatitis from the lacquer but 83% of these reactions resolved with continued exposure."

As a child, my grandmother once accidentally used a poison oak stem to roast a hotdog over a campfire. She hadn't cooked it hot enough to denature the oil, and she reacted to it internally, which required a hospital visit.

Granted, consuming it is the worst-case scenario, but exposure to those oils can be life threatening.

There are people eating poison oak salad to try to make themselves immune:

https://www.wsj.com/style/eat-poison-ivy-oak-immunity-3207ec...