A school-based survey has found that 8.5 per cent of students report they are allergic to one or more foods.
The finding is an interim one, based on only 2800 participants in an online survey that is expected to grow to 30,000 students aged 10 to 18.
This year is the first time that a question on food allergies has been included in the long-running CensusAtSchool survey project hosted by the Auckland University statistics department, with Statistics New Zealand and the Education Ministry.
The question was added because of the widespread belief that the prevalence of food allergies is increasing. Its inclusion has raised hopes New Zealand may at last get some hard data on the size of the problem.
"The exciting thing about the CensusAtSchool survey is that inclusion of the question on food allergy reflects the impact this is having on children," said Allergy New Zealand chief executive Penny Jorgensen.
"Also, this is only preliminary data. The survey expects up to 30,000 responses so we really look forward to the final data once it is available."
Food allergies are different from food intolerance. Allergies, which usually occur within minutes of contact with the food, involve an exaggerated immune response that can cause symptoms, varying in type and severity, such as itchy skin, swelling, wheeze, vomiting and diarrhoea.
In the worst cases patients can suffer anaphylactic shock, a rare, life-threatening reaction that can involve constricted breathing and a collapse in blood pressure.
In some cases simply touching the food, rather than eating it, is enough to provoke a reaction.
Ms Jorgensen said self-reported rates of food allergy were always higher than rates based on diagnosis by a doctor. However a study of Melbourne 1-year-olds found 10 per cent had a test-proven food allergy.
The commonest food allergies in New Zealand children are to milk, eggs, peanuts and tree nuts.
A pilot survey of children at Plunket clinics found 44 of 110 under 5 had had adverse reactions to food.
"The most alarming aspect of this was that only four had been investigated for food allergy."
Young people's allergies
8.5 per cent of students aged 10-18 report having at least one food allergy
3.5 per cent allergic to dairy foods
2.5 per cent peanuts
2 per cent eggs
1.9 per cent wheat, tree nuts, shellfish, fish or soy
Source: Preliminary results of NZ CensusAtSchool online survey of 2800 students