Physicians should use caution before subjecting children to painful allergy tests, and to avoid basing their diagnoses solely on these test results.
In a recent article in the journal, Pediatrics, Robert Wood of Johns Hopkins Children’s Center in Baltimore and Scott Sicherer of Mt. Sinai Hospital in New York City warn against using blood tests and skin-pricking tests as stand-alone diagnostic tools. The test should only be used to confirm suspicion of allergies in patients with no symptoms. They should never be used to look for allergies, they said.
That’s because skin prick and blood tests can only show that a person is sensitive to a particular substance. They can’t always predict if an actual allergic reaction would take place, or its severity. Nor are they completely reliable. For example, up to 8 percent of children will have a positive skin or blood test for peanut allergies, but only 1 percent of them will actually have symptoms. And some children with negative test results will actually have allergies—undiagnosed allergies, particularly food allergies, can be dangerous, even fatal.
The researchers advise physicians to only use skin prick and blood tests to:
• Determine vaccine allergies (through skin tests only).
• Confirm a suspected trigger after seeing reactions suggestive of an allergy. For example, a child with asthma should be tested for allergies to environmental triggers such as pollen, mold, pet dander, or dust mites.
• Monitor the course of established food allergies, via periodic testing, to determine if someone is still allergic or outgrowing a food allergy.
• Confirm an allergy to insect venom after a sting causes a life-threatening allergic reaction.
Physicians should not use these allergy tests as general screening tools, to test for drug allergies, or to test children with known allergic reactions to specific foods.
According to the National Institutes of Health, almost 3 percent of Americans (nearly 8 million people), and at least 6 percent of children, have at least one food allergy.