Type 38 Arisakas (and several other Japanese guns of the 20th c) were coated in Uruishioil a finish derived from a type of sumac tree. This finish would cause individuals to get horrible rashes when they came in contact with it (under certain conditions), similar to a poison ivy outbreak.
These reactions would primarily happen when these rifles were being cut down or refinished. After the end of WW2 numerous former soldiers in America were admitted into hospitals when they broke out with rashes as a result of them attempting to sporterize captured rifles they had brought back from Japan.
There wasn’t an insidious intention behind the use of the Uruishioil, it was simply a common finish used in Eastern Asia at the period.
Mosin Crate Short:
From what I read it was problematic in either a liquid form or when being sanded or cut. I didn’t see any mention of it being harmful once applied under normal function.
But going back I can see I should reword the first paragraph as when read alone it could give that impression.
Cool. Yeah that totally tracks with what I have read about the stuff.