In a recent episode of Big Bang Theory, Howard waxes nostalgic to when
he hid under a desk in his room, ate peanut M&Ms, and went into his
first anaphalactic shock. After returning from the hospital, he
celebrated by eating some Snickers, which caused him to suffer a
second anaphalactic shock. We’ve seen other evidence of Howard’s
peanut allergy as well.
Howard then says he learned about his allergy after his third Almond Joy.
The problem? Peanuts are legumes, not nuts. A peanut allergy is
completed unrelated to a true nut (tree nut) allergy.
It’s possible that Howard is allergic to both and/or the traces of
peanut found in Almond Joy (since they’re manufactured in the same
facility that makes peanut candies) trigger his allergy.