It is possible for adults (who were not allergic as children) to develop a new allergy to peanut. In these cases, peanut allergy tends to be less severe, and is likely caused by the oral allergy syndrome as a result of birch allergy.
Peanut allergy is much less common in other parts of the world compared to Westernized countries. Despite peanut being a major food source in Asia, peanut allergy is uncommon. This is thought to be due to the common method of cooking peanuts in Asia, frying and boiling, which makes the food less allergenic. Dry roasting, the common method of cooking peanuts in the United States has been shown to make peanuts more allergenic.