How common is peanut allergy among young people in the United Kingdom? Roughly 1 in 50 seven-year-olds in one large study showed an allergy to peanuts or tree nuts. This research follows about 14,000 participants from birth. Researchers use skin prick tests and food challenges to identify genuine allergies. Medical histories provide additional evidence. Umbilical cord blood samples check whether sensitization was present at birth. The cord blood showed no signs of peanut allergy at birth. That means sensitization develops sometime after. About 40 percent of peanut-allergic participants also reacted to tree nuts. One third outgrew their peanut allergy before age five. Eczema in early infancy was linked to higher allergy risk. Skin creams containing peanut oil applied to rashes may play a role. A possible connection to soya formula in infancy was also found.