Constitution rating and allergies

[Driddle]

How about this, then?: It's not that you have an allergy, but rather how you keep moving on through the day regardless that reflects on your Con score. -- "I've wrestled the tarrasque to a standstill; darned if I'm gonna let a few sniffles keep me in bed!"

 

[Umbran]

This is one of these areas where D&D physics/biology doesn't match the real world. Immune systems well adapted to earlier, less sanitary times are more likely to have allergic reactions than those adapted to the antiseptic modern world.

Well, we don't know that for sure, because there are no immune systems adapted to the modern, antiseptic conditions. Those conditions simply haven't existed for long enough to know the characteristics of a system adapted to them. And that's assuming the system can be adapted - it may be that a system adapted to have few allergic reactions in an antiseptic condition may not be able to produce results when faced with a pathogen.