Childhood food allergies are on the rise, said a US study that suggested twice as many children are allergic to food as the US government has previously estimated.

About eight per cent of children under 18, or 5.9 million children in the US, have some kind of food allergy, said the study published in the journal Paediatrics.

That is about double the latest data from the US Centers for Disease Control and Prevention which showed a 3.9 per cent infection rate, or about three million children with allergies in 2007.

“Based on our data, about one in every 13 children has a food allergy,” said lead author and paediatrician Ruchi Gupta of the Northwestern University Feinberg School of Medicine.

“What’s more, nearly two out of every five affected children suffer from a severe food allergy. For these children, accidental ingestion of an allergenic food may lead to difficulty breathing, a sharp drop in blood pressure, and even death.”

The findings came from a survey of 40,000 households in the US. Researchers found that African-American and Asian-American children were less likely than white children to receive a formal diagnosis of food allergies, but were more likely to display a “convincing history of food allergy”.

Future studies will be aimed at understanding some of the geographical and racial trends observed, said Dr Gupta.

“By understanding why some children are affected by food allergy while others are not, we can begin to better focus our efforts on finding a cure.”

The CDC lists eight types of foods as responsible for 90 per cent of food allergies in young people: milk, eggs, peanuts, tree nuts, fish, shellfish, soy and wheat.

Scientists are unsure why children develop food allergies, which they often grow out of, but studies indicate food allergies may be on the rise among US youths, the CDC said in its latest 2008 report on the subject.