Application of purified native and recombinant allergenic molecules into IgE antibody assays can improve analytical sensitivity and specificity for selected allergen specificities. They enhance analytical sensitivity by allowing assays to detect IgE antibodies with a lower limit of quantification (LoQ) to missing or poorly represented allergens in diagnostic extracts that are commonly used in vivo and in vitro. Use of selected allergenic molecules can help improve the clinician's prediction of the risk of a serious allergic reaction to stable allergens. They can provide diagnostic information to determine if a provocation challenge (e.g., oral food challenge) is indeed mandatory or not necessarily needed to support the final diagnostic decision. Suspected cross-reactivity based on the clinical history can be adjudicated by analyzing IgE antibodies to allergenic molecules from cross-reactive protein families. Finally, genuine primary sensitization can be identified by IgE antibody responses that are measured to selected allergenic molecules which are present in only one particular allergen source. After allergen-specific IgE detection, careful interpretation is required by the physician who knows the patient's history. Applying single allergen molecules, positive IgE antibody results are still only relevant in the case of corresponding objective symptoms. Subsequently, clinical relevance of such an IgE antibody test result must be determined by the clinician and not by the test itself. Because of their comprehensive nature, allergen extracts will remain the principal allergen source for diagnostic in vivo and in vitro assays of IgE antibody for many years. Judicious use of individual allergenic molecules in serum IgE assays may provide their most cost effective and efficient application for establishing a definitive diagnosis of human allergic disease.