False negative reaction:
(1) extract produced with low potency
(2) extract lacking the specific allergen that the patient is sensitive to
(3) loss of potency during transport and storage
(4) failure to include an allergen in the test battery
(5) medication reducing the allergic response
(6) disease reducing the allergic response
(7) age-related decrease in skin reactivity (infant, elderly)
(8) improper skin puncture technique
(9) improper interpretation of the reaction
False positive reaction or greater than expected:
(1) dermatographism or physical urticaria
(2) allergic reaction to stabilizer or other allergen in extract solution
(3) excessive allergen concentration
(4) chemical irritant, especially in sensitive skin
(5) non-specific enhancement related to an adjacent strong reaction
(6) improper interpretation of the reaction
Positive and negative controls should be used to help interpret the reaction.
