The UPDATE 2018-2022 has been published and can be downloaded for free from this website. It is an addendum to and an update of Patch Testing, 4th edition (ISBN 978-90-813233-4-5). The file contains information on 255 new allergens, both chemicals described as contact allergens after publication of the book and systemic drugs causing various forms of drug eruptions verified by positive patch tests or occupational allergic contact dermatitis. The update also provides updated information on patch testing for over 120 chemicals which were already present in the 4th edition.