Although I myself do not do clinical skin testing for food (or other)
allergies, my allergist colleagues have told me that they will skin test
infants under certain conditions.  Very young children (especially those
under 1 year, and perhaps up to 2 years) have "funny" skin and may not test
reliably.  It is felt that mast cells (which release histamine and other
chemicals in response to allergen challenge, resulting in wheal and flare
reactions) do not always migrate well into the skin at an early age, and this
may result in false negative skin tests.  A positive skin test would most
likely indicate an allergy to the tested substance, but a negative test would
not necessarily mean the infant was not allergic.  Therefore, if
sensitivities to foods were strongly suspected in an infant, allergen
avoidance might still be recommended in the presence of a negative test.
 Skin tests are helpful to confirm a suspected allergy, but are not reliable
enough to rule out a negative reaction in young babies.

In older individuals, however, negative skin tests are useful to rule out
food allergies and false positive skin tests become a problem with diagnosis.
 Double-blind, controlled oral food challenges following elimination of a
food from the diet remain the gold standard for diagnosis of food allergies.

Marty O'Donnell, PhD      [log in to unmask]