The ingredient in Caldari tea that people seem so concerned about is a product of the evergreen Kresh tree. The Kresh tree was originally native only to the Caldari homeworld, where it was often the only green thing that survived the harshest of winters in a (semi) edible state.

Resistance to the toxin in Kresh became a pro-survival trait. Those who were especially susceptible to it certainly perished more quickly in winter - either from starvation or toxin induced suffocation. The rest of us inherited resistance and, I think, it was to retain that resistance that Kresh became a ritual part of our diet.

The Achuran people joined the State only much later and, therefore, whilst both of our cultures enjoy a lively interest in tea and tea-related ritual, they have never had occasion to acquire the immunity to it. Incidentally, the tea that you can buy in stores and that all Caldari are taught to prepare is the non-toxic variety. Only highly trained specialists are ever taught the tea that is the central component of the "Tea Maker Ceremony", where special tea and special preparation is used to raise the strength of the toxicity to the level that will kill even Caldari.

As a matter of course, Non-Caldari ought to avoid any product with the word "Kresh" in the title - even though most people can safely metabolise the amount of Kresh in a single cup of tea or an appetizer at a restaurant with little more effect than a splitting headache or a cough.