Below are the most important presentations and lectures I have given over the years listed. Of these, only 12 were at  conferences abroad: 1987 Rome (2 lectures), 1988 Heidelberg, 1989 Florence (3 lectures), 1989 Vienna, 1990 Stockholm, 1991 Cardiff, 1996 London, 1997 Brussels and 1997 Ghent. Many of the presentations were about the side effects of cosmetics, the subject of my 1988 dissertation. After 1997, I have'nt attended any conferences in other countries anymore. I absolutely hate travelling, I never sleep a wink the first night in a strange bed and searching for everything (taxi, toilet, dining room, where to hand in your slides, restaurant et cetera) is not easy for me. Also very important: I don't learn anything at such conferences. There are very few people who can give a decent presentation. Most of my colleagues present way too much information and/or give a very dry story that makes you fall asleep (this has been the subject of research, it really happens very often). Moreover, the English of authors from (some) non-English speaking countries is often so terrible that you hardly understand anything. Academic colleagues are of course delighted to be able to attend a conference (because they are away from work), but as a practicing dermatologist I had a loss of income in addition to the conference costs and the practice was always busier after returning. But I have to be honest: I don't feel at all comfortable in an unfamiliar environment and with people I don't or hardly know. And after such a lecture I saw them sneaking up on me from the corner of my eye, the colleagues who wanted to talk one on one: 'Professor DeGroet, may I ask you a question?' Horror. No international conferences for me.

Between 2010 and 2012 (and also later), I have given, often together with Johan Toonstra, a large number of lectures for pedicures after the books Feet and Skin (2009) and Nail Disorders (2010) were published by Bohn Stafleu van Loghum (BSL). The most enjoyable were the lectures in the Jaarbeurshallen in Utrecht, which were organized by BSL and where up to 400 foot care providers were sometimes present. But at smaller locations, at events organized by the pedicures themselves, there was almost always something wrong with the equipment and sometimes we could only start after 1.5 hours. Also, the projectors or screens were often less than adequate, so that the spectators were shown blurry pictures, which is deadly for an educational dermatology presentation. That also applied to my last lecture in 2017 in Amersfoort, which was organized by the Dutch Cosmetics Association. After that I had enough and decided at that point to close this part of my career. Incidentally, my social skills didn't improve either and that obviously also played an important role. A pity, really, because the presentations, without any exception (except for those vague images), went very well, I made sure that there was always a lot to laugh about and the reviews were always positive.

This patient had mild eczema on the left half of the back consisting of erythema (redness). He had been treating this area of skin for many weeks with an ointment containing lidocaine (a local anaesthetic), which is used to treat pain and itching of the skin. Previously, the patient had had shingles there (herpes zoster) and this had left him with long-term pain, the so-called post-herpetic neuralgia. Prior to patch testing, the dermatologist requested that he perform a ROAT (Repeated Open Application Test) with the ointment in the right elbow crease. After 2 weeks, an itchy and erythematous eczema developed here, which is (almost) convincing evidence of contact allergy to the ointment. Afterwards, patch tests were performed with all components of the ointment to identify the allergen in it (which turned out to be lidocaine).

List of lectures and presentations

• Kathon CG: Risk of sensitization. 2nd International Meeting on Cosmetic Dermatology. Rome, 19-22 Mei 1987
• Adverse effects of cosmetics: A survey among clients of beauticians. 2nd International Meeting on Cosmetic Dermatology. Rome, 19-22 Mei 1987
• Hoevaak berust een bijwerking van cosmetica op allergie? Wetenschappelijke vergadering van de Nederlandse Vereniging voor Dermatologie en Venereologie. Groningen, September 1987
• The allergenic ingredients in cosmetics. First meeting of the European Contact Dermatitis Society. Heidelberg, 27-29 Mei 1988
• Kathon CG: praktische informatie voor de dermatoloog en de voor dit conserveermiddel allergische patient. Wetenschappelijke vergadering van de Nederlandse Vereniging voor Dermatologie en Venereologie. Maastricht, 1 Oktober 1988
• Kontaktallergie voor cosmetica. Wetenschappelijke vergadering van de Nederlandse Vereniging voor Allergologie. Utrecht, 18 Maart 1989
• The disadvantage of water: the need for preservation. IFSCC-NVCC Joint Conference In Between Congress. "Waterology - The role of water in cosmetic science". Amsterdam, 10-12 April 1989
• Nystatin allergy: petrolatum is not the optimal vehicle for patch testing. First Congress of the European Academy of Dermatology. Florence, 25-28 September 1989
• The prevalence of contact allergy in atopic patients. First Congress of the European Academy of Dermatology. Florence, 25-28 September 1989
• Contact allergy to cosmetics. First Congress of the European Academy of Dermatology. Florence, 25-28 September 1989
• Ingredient labelling in the EEC. 3rd International Congress of the International Society for Cosmetic Dermatology. Wenen, 27-29 Oktober 1989
• Contactallergie voor Mitomycine C. Wetenschappelijke vergadering van de Nederlandse Vereniging voor Allergologie. Groningen, 17 maart 1990
• 31e Federatieve vergadering van de Federatie van Medisch Wetenschappelijke Verenigingen in Nederland. Leiden, 19 april 1990
• Systemic contact dermatitis from intravesical instillation of the antitumor antibiotic Mitomycin C. 8th International Congress on Contact Dermatitis. Stockholm, 17-19 mei 1990
• De relatie tussen atopie en contactallergie. Nederlandse Vereniging voor Allergologie. Amersfoort, 29 september 1990
• Cutaneous hazards associated with the use of cosmetics. Congress: The Environmental threat to the skin. Cardiff, 14-17 april 1991

Allergic contact eczema due to the fragrance raw material Lyral (official name: hydroxyisohexyl 3-cyclohexene carboxaldehyde) in a spray deodorant. This was one of the first cases of allergy to this substance, which would later become the most common perfume allergen. The product was banned in the European Union several years ago. At the time I received the photo from Prof. dr. Peter J. Frosch from Germany

• Aard en frequentie van huidafwijkingen door intravesikale instillatie van mitomycine C. Wetenschappelijke vergadering van de Nederlandse Vereniging voor Urologie. Arnhem, 3 mei 1991
• Epidemiology and clinical aspects of cosmetic side effects. Medical Aspects of Cosmetics. 6-7 juni 1994
• Contacturticaria syndroom en het beroep. Cursorisch Onderwijs: Contactdermatosen en Arbeidsdermatologie. Congrescentrum de Eenhoorn, Amersfoort. 1 oktober 1994
• Kriskras door de Dermatologie: Diagnose en Therapie. Duodagen Dermatologie, Werkgroep Deskundigheidsbevordering Huisartsen, Conferentiecentrum Bos en Ven, Oisterwijk. 14 april en 27 april 1994.
• Kliniek van chronische veneuze insufficientie. Districts Huisartsen Vereniging, 's-Hertogenbosch. 8 februari 1995
• Fragrances as a cause of contact dermatitis in cosmetics. Clinical aspects and epidemiological data. Jadassohn Centenary Congress, London. 9-12 October 1996.
• Dermatologie in diaperspectief. Papendal, Arnhem. Bossche nascholingsdagen, 10 en 24 april 1997
• Adverse reactions to fragrances. Intensive Course in Dermato-Cosmetic Sciences. Brussel, 23 september 1997
• Fatal attractiveness: the shady side of cosmetics. Vijfde Symposium van de Belgian Contact and Environmental Dermatitis Group. Gent, 27 september 1997
• Bijwerkingen van parfumgrondstoffen: hun minder rooskleurige zijde. Symposium Contactallergologische Actualiteiten (ter gelegenheid van het 25-jarig bestaan van de afdeling Arbeidsdermatologie van de VU Amsterdam). Amsterdam, 28 november 1997
• Fatale aantrekkelijkheid: de schaduwzijde van cosmetica. Minisymposium ter gelegenheid van het afscheid van dr. G. Smeenk. Deventer, 8 januari 1998
• Bijwerkingen van cosmetica - un update. Academisch Ziekenhuis Utrecht, afd. Dermatologie. Refereeravond, 3 december 1998
• Cosmetica en parfums. Themadag Contactdermatosen. Amersfoort, 10 september 1999
• Clinical relevance of contact allergy to preservatives and fragrances. 8th Congress European Academy of Dermatology and Venereology. Amsterdam, 2 oktober 1999
• Samenwerking tussen huisarts en huidarts. Symposium “Dermatologie voor huisartsen”. Kasteel Maurick, Vught, 28 juni 2001
• Hoe schrijf je een wetenschappelijk artikel? Voordracht voor arts-assistenten in opleiding tot dermatoloog, Groningen, 28 december 2006
• Dermatitis herpetiformis: enkele vragen uit de CBO-richtlijn. Refereeravond Universitair Medisch Centrum Groningen, Groningen, 8 maart 2007
• Presentatie UMCG Groningen, afd. Dermatologie, naar aanleiding van het uitkomen van Patch Testing, 3^e December 2008
• Presentatie UMCG Groningen, afd. Dermatologie, naar aanleiding van het uitkomen van Casuïstiek in de Dermatologie, deel 1, 26 oktober 2009
• Dermatologie voor Voetspecialisten. Presentatie voor pedicures, Jaarbeurs Utrecht, 10 december 2009
• Psoriasis. Presentatie voor pedicures, Jaarbeurs Utrecht, 10 december 2009
• Dermatologie voor Voetspecialisten. Presentatie voor pedicures, Jaarbeurs Utrecht, 18 maart 2010
• Psoriasis. Presentatie voor pedicures, Jaarbeurs Utrecht, 18 maart 2010

During one of my lectures for pedicures at the Jaarbeurshallen in Utrecht

• Casuïstiek in de Dermatologie. Nascholing voor huisartsen. ’s-Hertogenbosch, 12 mei 2010
• Casuïstiek in de Dermatologie. Nascholing voor huisartsen. Groningen, 8 juni 2010
• Casuïstiek in de Dermatologie. Nascholing voor huisartsen. Emmeloord, 22 juni 2010
• Dermatologie voor Voetspecialisten. Presentatie voor pedicures, Jaarbeurs Utrecht, 8 december 2010
• Presentatie voor pedicures, Jaarbeurs Utrecht, 8 december 2010
• Nagelafwijkingen bij psoriasis. Presentatie voor pedicures, Jaarbeurs Utrecht, 14 december 2010
• Presentatie voor pedicures, Jaarbeurs Utrecht, 14 december 2010
• Eczeem en psoriasis. Presentatie voor pedicures, Zwolle, 4 februari 2011
• Presentatie voor pedicures, Jaarbeurs Utrecht, 17 mei 2011
• Nagelafwijkingen bij psoriasis. Presentatie voor pedicures, Jaarbeurs Utrecht, 17 mei 2011
• Eczeem en psoriasis. Presentatie voor pedicures, Deventer, 18 juni 2011
• Vaatafwijkingen en schimmelinfecties. Presentatie voor pedicures, Apeldoorn, 1 oktober 2011
• Vaatafwijkingen en schimmelinfecties. Presentatie voor pedicures, Apeldoorn, 9 december 2011
• Vaatafwijkingen en schimmelinfecties. Presentatie voor pedicures, Sneek, 16 maart 2012
• Contactallergie voor cosmetica. Nascholingsdag Nederlandse Vereniging voor Huidtherapie, Ede, 3 november 2012
• Allergie voor cosmetica. Voordracht voor Pharmaciae Sacrum, de vereniging van studenten Pharmacie te Groningen, ter gelegenheid van de 131ste Dies Natalis. Groningen, Huis de Beurs, 13 februari 2013
• Voeten en schimmels. Seminar Dermatologie voor de Pedicure, 11 maart 2017, Nieuwegein
• Voeten en nagels. Seminar Dermatologie voor de Pedicure, 11 maart 2017, Nieuwegein
• Allergische reacties op tandpasta’s: frequentie, allergenen, klinisch beeld en testmethodiek. Seminar Dermatologie en Cosmetica ‘Tussen neus en lippen’, PMS Cosmetica, Amersfoort, 12 april 2017

In all my scientific and non-scientific lectures I have always built in a portion of humour. Without occasional laughter, the minds of many listeners will wander and some, depending on the circumstances of the presentation, of course, will doze off or fall asleep. Part of that was not taking myself too seriously and joking about some of my less attractive qualities, such as vanity, lack of modesty, or stinginess. I always like puns too. I found a fine example in a speech I gave as chairman of the medical staff of Carolus Hospital on the occasion of the farewell of the chairman of the supervisory board of the hospital. I have printed the part of the speech in question below. Typical De Groot humour! Too difficult for me to translate into English while retaining the humour, sorry!

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