De Groot has written a total of 30 books (22 titles, one with 4 editions, one with 3, and three books with 2 editions, and including his scientific autobiography), of which 7 are international books. Apart from “Unwanted Effects of Cosmetics and Drugs used in Dermatology” and “Patch Testing”, these are “Essential Oils: Contact Allergy and Chemical Composition” (2016, ISBN 9781482246407), “Monographs in Contact Allergy, Volume 1. Non-fragrance Allergens in Cosmetics” (2018, ISBN 978-1-138-57325-3 and 9781138573383), ”Monographs in Contact Allergy, Volume 2. Fragrances and Essential Oils” (2019, ISBN 9780367149802), ”Monographs in Contact Allergy, Volume 3. Topical Drugs” (2021, ISBN 978-0-367-23693-9), and ”Monographs in Contact Allergy, Volume 4. Systemic Drugs” (2022, ISBN 978-0-367-43649-0), all published by CRC Press Taylor and Francis Group, Boca Raton, Fl.,U.S.A.
The other books that he wrote, mostly together with his friend and colleague Johan Toonstra MD, PhD, are general dermatology books in Dutch for medical students, general practitioners, “skin therapists” (huidtherapeuten, a paramedical profession largely restricted to The Netherlands) and pedicures and podotherapists; in addition, he wrote a booklet “Living with Eczema” for patients with atopic eczema and their parents.