Allergen-specific immunotherapy (SIT) is the only allergen-specific treatment for allergy. It can prevent progression of the disease and has a long-lasting therapeutic effect. Since SIT is allergen-specific, the identification of the disease-eliciting allergen is an essential prerequisite for the accurate prescription of treatment. Diagnostic tests based on allergen extracts consist of mixtures of various allergens of which some are specific for the allergen source and others occur as cross-reactive allergens in various unrelated allergen sources. It may therefore be difficult and sometimes impossible to identify the disease-causing allergen with such tests, particularly in patients who are sensitized to more than one allergen source. Sensitization to pollens from olive, grasses, and Parietaria in the Mediterranean area is frequently treated with SIT. Here, we describe allergen molecules from these sources that can be used for component-resolved diagnosis of allergy to facilitate the selection of patients for SIT and monitor the immunological effects of treatment.