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I've heard this claim a lot (usually by schools who take a lot of measures to prevent peanut exposure in the classrooms and lunch area, or by parents of allergic children), but is there any scientific evidence that non-contact exposure to peanuts or peanut butter would produce any significant symptoms in an allergy sufferer? If I'm eating a peanut butter sandwich on a bus, and the kid next to me is allergic, do I need to worry about him keeling over?

CoffeeDay
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smooshie
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    I suppose it could trigger some kind of a pavlovian response (people with peanut allergies could learn to associate the smell of peanuts with becoming sick and therefore start to feel sick when they smell peanuts). – GordonM Nov 19 '15 at 11:42

1 Answers1

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It's basically false.

The smell of peanut butter is caused by pyrizines, which are not proteins. It is the proteins that trigger allergic reactions. So the smell of peanut butter sandwich from the next table should not cause an allergic reaction.

BUT people can have reactions when they inhale food proteins that they are allergic to. This can be seen when food is actively cooked, when powdered or crushed forms become aerosolized, or in other situations when proteins are released into the air.

Link to relevant study

The latter case generally only happens in enclosed spaces with large amounts of peanut material, such as an airplane where dozens of people are popping open peanut packets (study based on self-report) or inside a kitchen where peanut oil is being used to fry things and particles of the oil are being thrown into the air.

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Sean Duggan
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    This doesn't mean it's not triggered by the smell of peanuts. It's possible that in virtually all conditions where you smell peanuts there are aerosolized proteins too. While it technically wouldn't be the odor causing the problem, the odor would still be a reliable indicator and I'd say the claim was true in that case. – William Grobman Nov 18 '15 at 18:18
  • ... Actually, no. As per the first two links, most cases where you smell peanuts don't involve the proteins, but pyrizines, and those don't trigger the peanuts. The smell is not what causes the allergic reaction, but the proteins, which can be airborne, but only in rare cases. The allergic reaction requires contact, if only with the aerosolized particles. – Sean Duggan Nov 18 '15 at 18:21
  • That's fair. It would be nice if you quoted the relevant passages from those links to address that though. When I read your answer without checking sources, it appears to merely be stating that the claim is technically false. – William Grobman Nov 18 '15 at 18:24
  • :) I guess, from my viewpoint, that's exactly what the quoted paragraph above says. – Sean Duggan Nov 18 '15 at 18:39
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    I shared @WilliamGrobman's concern. The quoted text is really saying "*Absolutely true*, except for a minor technicality. If you can smell it, you are in danger, even though strictly speaking the smell itself isn't the cause." **BUT** when you look at the *empirical* evidence (from the study, moderately small sample, peanut butter only), the answer is really "**NO**, spending ten minutes with peanut butter a foot from your face is fine". – Oddthinking Nov 19 '15 at 11:55
  • Hmm... whereas, to me, the quoted paragraph is saying that it's "not true *except* in extreme conditions, so it's false, but *technically* potentially true" in the same way that smelling bitter almonds technically means you might have been poisoned by cyanide since it's possible someone was spritzing it around. – Sean Duggan Nov 19 '15 at 12:24
  • Part of the question was "any scientific evidence that non-contact exposure to peanuts or peanut butter would produce any significant symptoms in an allergy sufferer". Part of your answer "people can have reactions when they inhale food proteins that they are allergic to". The only scientific evidence in your answer: "Casual exposure to peanut butter is unlikely to elicit significant allergic reactions. " – Oddthinking Nov 19 '15 at 12:54
  • I think the key aspect is "non-contact exposure to peanuts". Unless the peanut is in the air and you are coming in contact with it, there is not an allergic reaction. Do you feel that I need to make that more clear in my answer? – Sean Duggan Nov 19 '15 at 12:57
  • I think most people would consider inhaling to be "non-contact". I think in your answer, you should discard the unsubstantiated claims of allergyhome, and stick to empirical evidence. – Oddthinking Nov 19 '15 at 17:20
  • I will take a look at it tonight when I get home http://junkfoodscience.blogspot.com/2008/02/food-fears-run-amuck-government-outlaws.html?_sm_au_=iHVWF4S6L4MSRsjq looks like it might provide some more substantive evidence and I will now edit in bits from http://www.aaaai.org/ask-the-expert/peanut-air-travel.aspx where a study involving self-reporting within aircraft showed symptoms. – Sean Duggan Nov 19 '15 at 17:38
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    There is also the nocebo effect. If you are allergic to peanuts and you smell peanuts, you'll get an allergic reaction simply because you expect to get an allergic reaction. – John Dvorak Nov 22 '15 at 20:54
  • @JanDvorak: It's long enough in the future that I'm not really interested in putting the effort into ferreting it out, but there was another study where they were trying to determine the feasibility of the "a kid who ate a peanut butter sandwich was playing on the playground and left oil that caused a reaction" story, and found that there was a strong correlation between a present parent believing there was peanut oil, and symptoms in the child. I don't remember if the researchers relied on self-reporting in that case. – Sean Duggan Jul 12 '17 at 22:01