Identification of key alergen is vital for allocation to alergen immunotherapy. Molecular allergology (component resolved diagnostics – CRD) alows detailed molecular profiling of the polyclonal IgE in a particular patient. The use of molecular diagnostics in allergology improves sensitivity and specificity of diagnostic procedures, enables assessement of the prognosis and risk associated with a given type of sensitization and enables application of the most appropriate treatment, including qualification for specific immunotherapy. Diagnostic algorithms based on single or multiple molecular IgE tests, in contrast to diagnostic procedures based on alergen extracts, allow discrimination of genuine sensitization (sIgE against major allergens, markers of primary sensitization) from cross-reacting sensitization (sIgE against panallergens: profilins, polkalcins, tropomyosins). It has been hypotesized that patients without sensitization to major allergens may receive less therapeutic benefit from specific immunotherapy. Sensitization solely to panallergens do not constitute indication for immunotherapy. In some situations, especially in polysensitized patients, aplication of component-resolved diagnostics may increase the likelihood of sucesfull immunotherapy.