The enormous expansion of digital health will increasingly impact allergy practice and its scientific background. This development is so substantial that it generated a new area of interest, defined “Digital Allergology” and was first described with a position paper of the European Academy of Allergy and Clinical Immunology (EAACI). After describing pioneering initiatives, this introductory chapter continues as an extended summary of the book “Digital Allergology: from theory to practice.” The state of the art of digital allergology is described in terms of definitions and regulatory issues, e-Diaries for allergic rhinitis, allergic asthma, and wheezing disorders, chronic urticaria and atopic dermatitis, as well as drug allergies. Sections are also dedicated to wearables and social media, omics science, big data, and artificial intelligence. A description of how digital technologies are implemented in real life scenarios in large countries is also given, with a focus on Spain, Germany, and Australia.