Children belonging wealthy families are more at risk of developing a life-threatening allergy to peanuts.
Peanut allergy commonly causes breathing problems, but occasionally results in fatal anaphylactic shock.
The number of British youngsters with the condition is believed to have doubled in the past 20 years, with children of wealthy middle-class parents being the most vulnerable of all.
Researchers said this might be because children from wealthy backgrounds enjoy an excessively clean lifestyle, which leaves their developing immune systems unfamiliar with many germs.
When these children are later exposed to new irritants, including harmless foods such as nuts, their body is more likely to have an allergic reaction to them.
The new study examined 8,306 patients, 776 of which had some form of reaction to peanuts.
"Overall household income is only associated with peanut sensitization in children aged one to nine years. This may indicate that development of peanut sensitization at a young age is related to affluence, but those developed later in life are not," the Daily Mail quoted lead study author, allergist Dr Sandy Yip, as saying.
Researchers also found that peanut allergy was generally higher in males and racial minorities.
Until recently parents were told to avoid exposing their kids to peanuts until they were 3, to reduce allergy, but this official advice has been blamed by some experts for the rise of "nut hysteria."
Indeed, some doctors believe exposing children to peanuts early in their life could save them from developing an allergy by priming their immune system.