As someone suffering from (hazel-)nut allergy in a fairy mild form... consuming anything nut-contaminated is unpleasant to very unpleasant. It can be life-threatening to people more sensitive than me.
And breathing in dust can provoke an allergic reaction, but that will usually disappear quite quickly once the patient is able to breathe "fresh" (= allergen-free) air. And that is the problem with aeroplanes: there is no reasonable way to escape a dust cloud.