A Harvard professor of medical sociology has agreeably warned that increasing hysteria over nut allergies in kids bears the hallmarks of mass psychogenic illness (MPI) - described as "a social network phenomenon involving otherwise healthy people in a cascade of anxiety".

Writing in the British Medical Journal, Nicholas A Christakis cites the extreme example of when a potentially fatal peanut was "spotted on the floor of a school bus, whereupon the bus was evacuated and cleaned (I am tempted to say decontaminated), even though it was full of 10-year-olds who, unlike two-year-olds, could actually be told not to eat food off the floor".

He also explains the case of one of his own kid's school, which indulges in the traditional ritual of selling wrapping paper and candy to raise funds. He says: "This year parents in our school were told that they could no longer pick up their purchases from their children’s classrooms. Instead they had to pick up their orders from a loading dock at specified times, to avoid a danger to the children."

He continues: "The danger? Some of the orders contained sealed tins of festive nuts. Out of an overabundance of caution the school decided not to allow any of the items on the premises."

The facts are these, Christakis insists: "About 3.3 million Americans are allergic to nuts, and even more - 6.9 million - are allergic to seafood. However, all told, serious allergic reactions to foods cause just 2,000 hospitalisations a year (out of more than 30 million hospitalisations nationwide). And only 150 people (children and adults) die each year from all food allergies combined."

He adds: "Compare that number with the 50 people who die each year from bee stings, the 100 who die from lightning strikes, and the 45,000 who die in motor vehicle collisions. Or compare it with the 10,000 hospitalisations of children each year for traumatic brain injuries acquired during sports or the 2,000 who drown or the roughly 1,300 who die from gun accidents. We do not see calls to end athletics. There are no doubt thousands of parents who rid their cupboards of peanut butter but not of guns. And more children assuredly die walking or being driven to school each year than die from nut allergies."

Yup, sounds like a classic case of MPI, previously known as "epidemic hysteria", which commonly in small towns, factories and schools - described as easily susceptible to a fear of mass contamination - can "provoke anxiety to imagine a hidden, deadly danger in so innocent a thing as having a snack in kindergarten".

In reality, Christakis explains, MPI may actually exacerbate nut allergy problems, "resulting in children who, lacking exposure to nuts, are actually sensitised to them". The epidemic is fed, meanwhile by "efforts to reduce exposure to nuts [which] actually fan the flames, since they signal to parents that nuts are a clear and present danger" - which in turn "encourages more parents to worry, which fuels the epidemic".

Christakis reckons the cycle of "increasing anxiety, draconian measures, and increasing prevalence of nut allergies must be broken", and recommends treatment for MPI focussing on "the social and psychological nature of the epidemic" which apparently involves "providing reassurance ... [and] using a calm and authoritative approach".

Which, we reckon, can more or less be summarised as: "Your kids are not going to die from exposure to peanut butter. Now get a grip on yourself, you nutter." ®