A general monograph for allergen products has now been adopted by the European Pharmacopoeia Commission. It is based on the use of an In-House Reference Preparation (IHRP), which shall be used in the control of every production batch after appropriate characterization. This characterization will depend on the intended use of the product. When possible, the biological potency should be established by skin testing and expressed in biological units. The monograph is the first mandatory regulation in Europe for allergen products and will guarantee the consistent composition and potency of the products on the market.