For someone working regulary with KP an alergic reaction would be nothing compared to God knows what cancer could be caused after years of handling. A short, occasional exposure usually means nothing and it doesn't give the full image of what a chem can do. It's the worker who makes it that is affected in a visible way.
Better safe then sorry.
As somebody who regularly has to treat immediately life threatening allergic reactions,
whether it manifests as angio-oedema (swelling of the face, tongue and upper airways),
severe bronchospasm (wheeze) or cardio-vascular collapse, allergic reactions can
obviously be extremely dangerous and can kill.
This is not meant to minimise long term detrimental effects of exposure , but please don't underestimate
an allergic response.
Cheers