Indoor allergens: relevance of major allergen measurements and standardization.

Major allergen measurements have relevance for the standardization of allergen extracts for immunotherapy and for epidemiologic studies into the cause of allergic diseases. Standardization is still centered around overall IgE-binding potencies (biological standardization). Major allergen levels show significant correlation with IgE-binding potencies, but ratios of the two can differ 5- to 10-fold between individual extracts. Major allergen quantities needed for effective and safe subcutaneous immunotherapy are proposed to be between 5 and 20 microg per maintenance shot. Although this figure is not really based on dose-finding studies, it has reached the status of a guiding principle. It is necessary to add major allergen measurements to standardization requirements to design adequate dosage schemes and elucidate the dose-response relation between major allergen dose and therapeutic effect. This will also help clarify to what extent sublingual immunotherapy requires higher doses of major allergen. Fine specificity of different assays toward isoforms and other variants of single allergens often results in diverging allergen measurements. Standardization should be based on certified major allergen references and accompanying assays that are cross-reactive enough to recognize all variants to facilitate comparability. This will also ensure that primary and secondary prevention strategies aiming at regulating allergen exposure will stay on solid ground.