Opinion StatementPurpose of Review At present, in vivo allergy diagnosis and allergen-specific immunotherapy (AIT) are still based on allergens extracted from natural material. The inherent content and activity change of allergen source cannot be resolved, which impedes the standardization of AIT and limits doctors' desire to recommend it. Recent Findings With the increasing use of allergen molecules in allergy diagnosis, the molecular allergens in AIT are believed to be the future trend. However, the current clinical phase III trials are not satisfying. Improvements have been made in the field of allergen extracts or molecular allergens-namely extraction methods, adjuvants, recombinant allergen fragments, and personalized medicine. In this article, we review recent progress in allergens preparation for AIT, the needs for further development and possible technical solutions available through molecular allergology.