UK scientists believe they have discovered how peanuts cause allergies in so many people.
One in 50 children in England is allergic to peanuts
By studying the guts of mice, the Institute of Food Research team tracked exactly how peanuts are digested.
This told them how large amounts of peanut proteins travel quickly through the gut to the immune system and trigger an allergic response.
Their findings will appear in Biochemical and Biophysical Research Communications.
The team found that digestion through the stomach and small intestine produced large amounts of soluble protein but also large, intact structures made of protein.
They then labelled the proteins with gold so they could track their movement.
The peanut proteins were delivered at high speed through the gut via cells called M-cells.
M-cells are designed to deliver foreign bodies, including proteins, to the body's defence cells, which can mount a response.
Lead researcher Dr Claudio Nicoletti said: "Peanut proteins are delivered quickly, in large amounts and in highly immunogenic form to immune cells.
"This may be important in explaining strong allergic reactions to peanuts."
Peanut allergy can be so severe that only very tiny amounts can be enough to trigger a response.
Dr Nicoletti said: "These data suggest that peanut protein bodies, on the basis of their route of transport, resistance to digestion, shape and size, may play a crucial role in the sensitisation process."
David Reading, director of the Anaphylaxis Campaign, said: "This work sounds very interesting and may prove to be an important part of the puzzle.
"Food allergy is certainly on the rise. A report by the House of Commons Health Committee a few weeks ago established that one in 50 children in England is now allergic to nuts - almost a quarter of a million children.
"Allergies to other foods and substances also appear to be on the increase, and the result is a considerable burden for those affected.
"Anything that helps us to understand allergy, and perhaps to point us to better treatments, will be welcomed by these people."