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Prof. Dr. Wolfgang Remy, Dermatologische Klinik und Poliklinik, der Technischen Universität München, Biedersteiner Strasse 29, D-80802 München (FRG) In an interesting comment, recently published in this journal, Singh and Maibach [1] state that extensive research is still required to maximize iontophoresis for controlled systemic transdermal administration of charged, hydrophilic and large drug molecules. It has been known for a long time that even large molecules such as grass pollen allergens had been provided by topical iontophoresis [2]. Grass pollen allergen extracts are today believed to form a mixture of heterogeneous proteins and glycoproteins with molecular weights of 11,000 and 31,000 D [3]. Therefore, in a clinical study, 52 patients with allergic rhinitis relevant to five common allergens were tested by the method of iontophoresis in comparison to the skin prick test [4]. The results of both methods corresponded to a large degree (90%). Set against the results of the RAST, iontophoresis seems to show an even better comparison than the prick test (86% in comparison to 81%). Advantages of this method are the semiquantita-tive application of allergen (depending on time and intensity of electric current) and their harmless application (no pricking of the skin is necessary). In a further study we tested the permeability of intact skin for high-molecular-weight allergenic proteins from grass pollen extracts dependent on molecular size [5]. For this purpose a molecular-weight-fractionated grass pollen extract was tested using iontophoresis as well. The results proved percutaneous absorption of proteins and glycoproteins even with a large molecular weight of about 30,000 D. These results give rise to questions about the penetrant entry of the allergens through the skin, via the hair follicles, the sweat glands or across ‘leaks’ in the stratum corneum. References Singh J, Maibach HI: Topical iontophoretic drug delivery in vivo: Historical development, devices and future perspectives. Dermatology 1993;187:235-238. Abramson HA: Skin reactions. X. Preseasonal treatment of hay fever by electrophoresis of ragweed pollen extracts into the skin: Preliminary report. Allergy 1941;12:169-175. Cottam GP, Moran DM, Standring R: Physi-cochemical and immunochemical characterization of allergenic proteins from rye-grass (Lυlium perenne) pollen prepared by a rapid and efficient purification method. Biochem J 1986;234:305-310. Remy W, Siebenwirth J, Karl S, Szliska CH, Rakoski J: Perkutane Testung von Typ-IAllergenen mittels Iontophorese. Haut Ge-schlechtskr 1993;68: 512-516. Gauger J, Remy W, Wachter E, Vocks E, Jess-berger B, Rakoski J: Perkutane Iontophorese von