Taking an oral steroid like prednisone can help prevent asthma attacks for milder allergies, but that might not be sufficient for a severe peanut allergy.

Epinephren is not a gentle drug. You do not want to have to use an epi pen if you can avoid it. It causes the heart to race and result in lots of side effects that would make a flight extremely uncomfortable. I think it’s also metabolized quickly enough that a single dose is not going to last a whole flight.

I’m not an expert though, I just have multiple family members with moderate to severe allergies.