Measures imposed to reduce exposure to nuts are often based on irrational fears of nut allergies and are becoming increasingly sensationalist, according to Professor Nicolas Christakis from Harvard Medical School on bmj.com today.

A peanut on the floor of a school bus leading to evacuation and decontamination for fear that it might be eaten by the 10 year old passengers, and schools declaring themselves "nut free" by banning nuts, peanut butter, homebaked goods and any foods without ingredient labels, are just some examples cited in the article.  According to Christaki, there is no evidence that any of these extreme restrictions work better than more circumscribed policies or that they are worth the money and disruptions they create.

In the US, 150 people die each year from food allergies. This is compared to the 50 who die from bee stings, the 100 who die from lightening strikes, the 45,000 who die in motor vehicle accidents, and the 10,000 who are hospitalised for traumatic brain injury from playing sport. But these issues do not incur such extreme reactions, such as calling for an end to sport.

Christakis says that the "gross over-reaction to the magnitude of the threat" is very similar to mass psychogenic illness (MPI), previously known as epidemic hysteria.

Often seen occurring in small towns, schools and factories, these outbreaks of MPI involve healthy people in a flow of anxiety, most often triggered by a fear of contamination. Being around individuals who are anxious heightens others' anxiety.

These extreme measures to reduce exposure to nuts are fuelling anxiety in parents, leading to more sensitisation, and creating the very epidemic they are designed to stop. A recent study has suggested that early exposure to peanuts actually reduces, rather than increases the risk of allergy.

Christakis concludes by calling for a level-headed strategy to deal with this phenomenon before it spirals out of control.