[dorkness]

Hello, friends. I'm an author, largely ignorant of chemistry, who's trying to give some reality to a novel I'm writing. I'm looking for some sort of chemical or poison that cause rapid death to some people who come in contact with it but have no effect on other people. Sort of like some people have deadly peanut allergies, but I'm looking for something that would be difficult to make or acquire. I don't know if I'm in the right place for that, but I don't want to spam your forums. I appreciate all the help you folks can give to this outsider. 

[orgopete]

Typhoid and I think people can build a tolerance to strychnine.

[cheetahj]

I think what you want is gene weapons. I can hardly imagine any chemical have that effect.

[Borek]

Friend of mine has a very strong allergy to some chemical present in most cosmetics. He had to stop working as he couldn't cope with people (he got to ER several times because of his condition). At the same time it doesn't stop him from working hard in his garden. What I am aiming at is that people are sometimes allergic to quite unexpected things that are present around most of us all the time.

Also see http://en.wikipedia.org/wiki/Bruce_Lee#Death