"Allergy tests can help a clinician in making a diagnosis but tests by themselves are not diagnostic magic bullets or foolproof predictors of clinical disease," Robert Wood of The Johns Hopkins Children's Center in Baltimore, said in a statement. "Many children with positive tests results do not have allergic symptoms and some children with negative test results have allergies."
Undiagnosed allergies can be dangerous, even fatal, but over-reliance on blood and skin tests can lead to a misdiagnosis, ill-advised food restrictions or unnecessary avoidance of environmental exposures, such as pets, Wood said.
Blood tests and skin-prick testing should be used only to confirm suspicion and never to look for allergies in an asymptomatic patient.
Wood and Scott Sicherer of Mt. Sinai Hospital in New York said test results should be interpreted in the context of a patient's symptoms and medical history. If a food allergy is suspected, the patient should undergo a food challenge -- the gold standard for diagnosis -- which involves consuming small doses of the suspected allergen under medical supervision.
The findings are published in the journal Pediatrics.