Nearly one-third of Americans believe they have a food allergy but the prevalence is actually much lower, a U.S. review concludes.

Food allergies affect less than 10 per cent of the U.S. population, Dr. Jennifer Schneider Chafen of the VA Palo Alto Healthcare System in California and her colleagues concluded in Wednesday's issue of the Journal of the American Medical Association.

The researchers reviewed evidence on the diagnosis, management and prevention of food allergies in the U.S. based on national telephone surveys. The researchers also reviewed 72 studies that reported data on allergies to cow's milk, hen eggs, tree nuts, fish, and shellfish, which they say account for more than half of food allergies.

The prevalence of peanut allergies in U.S. children is similar to results reported in studies from Canada, Australia and the U.K.

Finding similar results from various places lends more support to the conclusion of the true prevalence, the authors said. 

Some of the common ways of testing for food allergies are flawed, the authors said.

The review found about eight per cent of children and five per cent of adults have a real food allergy.

The authors said people can outgrow childhood food allergies or develop new ones as adults.

They said some people don't understand the difference between food allergies that involve the immune system and food intolerances that generally do not. A headache from sulphites in wine or lactose intolerance to digesting sugar in milk are examples of food intolerance.

The research was funded by the U.S. National Institutes of Health and was commissioned to develop guidelines on food allergies.