"Standard tests" showed that 10% of eight-year-olds in a British cohort were sensitive to peanuts but only one in 50 was actually allergic when the children were challenged with the legumes.
Standard methods were defined as a skin prick test producing a wheal whose diameter was at least three millimeters greater than a negative control, and/or a IgE response of at least 0.2 kiloUnits of peanut allergen per liter of serum.
The serum immunoglobulin E (IgE ) response to a single peanut protein, dubbed Ara h 2, was able to distinguish between the sensitivity and allergy in most cases.
Avoiding peanuts only makes sense if child is really allergic.
Currently, a double-blind, placebo-controlled food challenge (DBPCFC) is the gold standard for diagnosing peanut allergy, but it's time-consuming, costly, and risks a severe reaction.
The diagnostic value of specific IgE to Ara h 2: the need for peanut challenges could be reduced by at least 50% http://buff.ly/UueEhx
Test Improves Peanut Allergy Diagnosis. MedPage Today, 2010.
Peanut allergy: Patients with a positive SPT greater than the 95% PPV do not need an Arah2 testing undertaken http://bit.ly/SwbwBQ
Peanut allergy: Diagnostic accuracy of sIgE to Ara h 6 in adults is as good as Ara h 2 http://buff.ly/1uU314i
Image source: Degranulation processes. Wikipedia, GNU Free Documentation License.