Whether you like them roasted, boiled, raw, or made into a butter for a sandwich filling, peanuts are a popular food. Unfortunately, they are also among the top eight foods most likely to cause an allergic reaction. About three million Americans are allergic to peanuts.

In the Western world, peanuts are often roasted before they are eaten. In Asia, most people eat their peanuts raw, boiled, or fried. Peanut allergies are very rare in Asia and therein lies a clue.

The high temperatures involved (320oF and above) in dry roasting peanuts causes chemical changes in the foods' amino acids which may promote an allergic response.

Dry roasted peanuts are more likely to trigger a peanut allergy than raw peanuts, according to an Oxford University study, which could explain the difference in the number of people allergic to peanuts in the West compared to the East.

But what is it about dry roasted peanuts that make them more allergenic? A new study conducted using mice may have found an explanation.

Purified proteins from raw peanuts and dry roasted peanuts were given to mice in three different ways. It was injected under the skin of some mice, applied to broken skin on others, and placed directly in the stomach for a third group.

The mice exposed to dry roasted peanuts had much greater immune responses — that is, responses characteristic of allergic reactions — compared to mice exposed to raw peanuts.

“…[T]he dry roasting causes a chemical modification of peanut proteins that appears to activate the immune system against future exposure to peanuts,” Dr. Amin Moghaddam, first author of the study, said in a statement.

“Allergies in people are driven by multiple factors including family genetic background and exposure to environmental triggers. In the case of peanut allergy, we think we may have discovered an environmental trigger in the way that peanuts are processed by high-temperature roasting,” he said.

The high temperatures involved (320℉ and above) in dry roasting peanuts causes chemical changes in the foods' amino acids. This effect, called the Maillard chemical reaction, kicks in as soon as foods reach temperatures above 140℉.

The researchers suggest that it is the products of the Maillard reaction in peanuts that may cause a strong allergic immune response.

Because this research is in its early stages and further research needs to be done to confirm these results, the researchers say it is premature to advise avoiding dry roasted peanuts and their products to prevent allergy.

However, if dry roasting does contribute to peanut allergies, can changes in the way peanuts are processed reduce the likelihood of peanut allergies?


“We think we have identified the chemical modifications involved in triggering an allergic response to peanuts, and are currently exploring methods…to eliminate these groups,” says researcher Quentin Sattentau.

The study was published in the Journal of Allergy and Clinical Immunology.