Food allergies rose 18 percent in American children between 1997 and 2007. However, this figure may be inflated by a lot of improper diagnoses. A study by a team of pediatric researchers found that the blood tests doctors so commonly rely on to determine food allergies may not be reliable.
Generally, skin prick tests are less than 50 percent accurate compared to double-blind oral food challenges and blood tests are even less accurate than skin prick tests. The authors of the study suggest that false-positive blood tests or skin prick tests are common, and over-reliance on these methods frequently lead to unnecessarily restrictive diets. In fact, many of the children in the study reported avoiding foods that they had never eaten, or had tolerated previously without a reaction, because of blood tests that told them they were allergic.
The study specifically examined the food allergy diagnosis of children with eczema, a skin condition that is often believed to be caused or exacerbated by food allergies. There is a 33 percent chance that a food allergy will trigger a skin reaction in children with moderate eczema. Researchers reviewed the medical charts of 125 children, aged 1 to 19 years. Ninety-six percent of participants had active eczema, and all had been previously been evaluated for food allergies based on immunoassay or skin prick test with positive results. The researchers then administered an oral food challenge, the gold standard in allergy testing in which the participant ingests a previously avoided food under close medical supervision and is then observed for an allergic reaction over two hours.
The researchers found that 89 percent of the oral food challenge tests were negative — meaning that 89 percent of the time, a food had been unnecessarily eliminated from a participant’s diet based on results of previous blood tests. Experts warn that when it comes to allergy testing, blind trust in blood tests is not wise as it can lead to an unbalanced, monotonous diet that may contribute to malnutrition. Clinicians suggest that children with suspected food allergies should be evaluated using a complete medical history, physical exam, and blood tests with food elimination as indicated, followed by observation of the effect of elimination. If there is any doubt of the allergy diagnosis, an oral food challenge should be performed under supervision of a qualified medical professional. Furthermore, doctors recommend that children with eczema should not be tested for food allergies until their eczema is controlled.
All parents are advised to consult a pediatric allergist and a pediatric dietitian before children are placed on a restrictive elimination diet to ensure they consume a nutritionally adequate diet to support optimal growth and development. Your kid may not be allergic to peanuts after all.