No, allergies happen when the immune system detects innocuous substances as a threat. In this case, their metabolism has trouble breaking down the drugs in their gut so it can have unintended consequences for them. They can’t metabolize some organic structures in their livers or lungs as fast or as much as we do. And unfortunately, we don’t even know what the toxic dose is.
E: Jesus, downvoting legit pharmacology in favor of ideology. What a time to be alive.