If you were to get a bad enough bite from a hognose, the reaction you get would have little to do with allegies.
You would "suffer" from the by-product of their venom - namely toxins that affect blood coagulation - the other toxins that affect blood pressure would likely not be noticed by a human.
Hognoses are technically considered venomous, just as garter snakes and most other colubrids are technically venomous. If you get bit bad enough, you will see mild effects from the toxins in the venom - it has nothing to do with an allergic reaction.
If people are worried about a ban, then the key to avoiding the ban is proper education as to what the risks, if any, are. Again, if you receive a bad enough bite from a heterodon, you will exhibit symptoms that are by-products of the toxins in the venom. The fact is that those toxins are not life threatening.
None of this is news - Bryan Grieg Fry openly discusses the toxicity of colubrid venom on his site and his forum. The fact is that all colubrids, with the exception of lampropeltis, pituophis, pantherophis and their immediate relatives, are technically venomous.