Dallas writes:

These peanut allergy people really have a tough life as peanut by-products
can be used in just about anything processed. There's a chance that eating
a bag potato chips could set him off if he didn't read the label or the
factory was sloppy in listing their ingredients or cleaning their
equipment.

I would bet the risk of incapacitation is too high in his case for the FAA
to be comfortable giving him a medical. Please let us know how it turns
out, I'm sure several of us are curious.

Since the FAA is so paranoid about so many other potential (but often
farfetched) causes of incapacitation, I should think this would make them
shiver with apprehension, but who knows?