Peanut allergies overstated

May 15 2007

Despite hundreds of families being told their children have peanut allergies every year, many of the children may be able to eat peanuts safely, a study by the University of New South Wales (UNSW) and Sydney Children's Hospital has found.

Peanut allergies occur in one in 200 infants, according to the Australasian Society of Clinical Immunology and Allergy.

"This is a really important finding," said Dr Brynn Wainstein, a Sydney Children's Hospital immunologist and MD candidate at UNSW.

"Because peanut allergies are potentially serious, requiring all sorts of restrictions, families can become very anxious when in fact, some of these families may be worrying unnecessarily," Dr Wainstein said.

The study, published in the journal Pediatric Allergy and Immunology, involved 84 children with a positive result to a peanut skin-prick-test.

If a child is potentially allergic to peanut, he or she will get a hive as a result of the peanut skin-prick-test. Allergists measure the size of the hive in millimetres.

In this study, a third of the children with a hive of eight millimetres - which has been found elsewhere to be predictive of having peanut allergy - were found not to be allergic to peanuts when they took a peanut challenge. A challenge involves eating peanuts in a hospital environment.

"Diagnostic tests for peanut allergy have poor sensitivity and specificity," the paper concludes. "Previously described diagnostic cut-off levels do not have general applicability."

Reasons for this may include variables such as the equipment used and the pressure administered by the practitioner during a skin prick test.

"There is a population of children who have never eaten peanuts – or worse, those that eat them everyday, then have a positive peanut skin test and are told not to eat them," said Dr Wainstein.

Dr Wainstein said many children who have never eaten peanuts and are found to have a positive peanut skin test are probably NOT allergic to peanut and will need a peanut challenge to determine if they are allergic.

"If the child is able to tolerate normal amounts of peanut every day then the result of any peanut allergy test is irrelevant."

Allergy practitioners may need to interpret results of allergy tests in the context of their own practices, the researchers found.

"If there is a positive result, people need to ask whether it might be worth a peanut challenge in a hospital environment, especially if their child has never had an allergic reaction to peanut before," Dr Wainstein said.

The co-authors of the report are Dr Anthony Yee, Donna Jelley and Mary Ziegler, all from the Sydney Children's Hospital and Associate Professor John Ziegler, a UNSW conjoint academic in the School of Women's and Children's Health, at the Sydney Children's Hospital.

http://www.unsw.edu.au