Peanut allergies have plummeted in children

> I don't think there are any physics reasons why it'd be impossible

There is extensive evidence that the incidence of severe peanut allergies is significantly increased by the practice of avoiding early exposure in the absence of particular risk indicators, which is why that practice is now advised against.(IIRC, some of the first targeted studies were motivated by observed differences in incidence between the US where early avoidance had become common and Israel where peanut-based puff snacks were a common thing to give to babies not long after starting solid food.)

That reminds me of my parents who most often use peanut oil for cooking. I was eating food cooked in peanut oil every day. I was astounded when I heard in elementary school that people could be allergic to peanuts.

There is no allergenic proteins left in peanut oil or it would burn and be rancid at room temperature. Your anecdata is not relevant here.

There are proteins left in raw pressed peanut oil (used for lower heat cooking and as a finishing oil, somewhat similar to EVOO), but not in highly-refined peanut oil (typically used for high-heat cooking/deep frying.)

Both will eventually go rancid at room temperature , though highly refined oil has a longer shelf life (both sealed and, even moreso, after the seal is broken.)