Dry roasted peanuts are more likely to trigger an allergy to peanuts than their raw form, suggests a study.
Specific chemical changes caused by the high temperatures of the dry roasting process are recognised by the body's immune system, priming the body to set off an allergic immune response the next time it sees any peanuts, the study noted.
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"This is the first time, to our knowledge, that a potential trigger for peanut allergy has been directly shown," said lead researcher Quentin Sattentau, a professor at the Oxford University in Britain.
The results might explain why in the West, where roasted and dry-roasted peanuts are common, there are far more people with peanut allergies than in the East, where peanuts are more often eaten raw, boiled or fried.
"Our results in mice suggest that dry roasted peanuts may be more likely to lead to peanut allergy than raw peanuts: the dry roasting causes a chemical modification of peanut proteins that appears to activate the immune system against future exposure to peanuts," first author Amin Moghaddam of Oxford University added.
For the study, the researchers purified proteins from dry roasted peanuts and from raw peanuts.
They introduced the peanut proteins to mice in three different ways - injected under the skin, applied to broken skin, and introduced directly into the stomach.
The mice that had been exposed to dry roasted peanuts generated greatly increased immune responses to peanuts, compared to mice that had been exposed to raw peanut proteins.
The immune responses seen were characteristic of allergic reactions.
The study appeared in the Journal of Allergy and Clinical Immunology.