NEW YORK (Reuters Health) - Between 1 and 2 percent of children in the U.S. and Canada may have allergies to peanuts or tree nuts, with the U.S. rates seemingly on the rise, two new studies suggest.Peanuts and tree nuts such as almonds and walnuts are the most common causes of severe, sometimes life-threatening allergic reactions to food in the U.S. Recent research has suggested that while the per