The book consolidates current facts on molecular allergology and highlights its advantages for modern allergy diagnostics. It begins by introducing the most important protein families with allergens of similar structure. Individual allergens primarily enhance the accuracy of IgE determinations, with detailed explanations of their testing variants. Using common allergen sources—such as inhalant, food, and insect venom allergens—the book illustrates the benefits and limitations of molecular allergy diagnostics in clinical practice. The final section presents potential applications of molecular allergology, such as the development of recombinant allergen vaccines or hypoallergenic foods. This book expands upon the successful contribution series "In Focus: Molecular Allergology" from the Allergo Journal by Springer Medizin and describes the emerging discipline of molecular allergology.