ROAT: morphology of ROAT on arm, neck and face in formaldehyde and diazolidinyl urea sensitive individuals CLAUS ZACHARIAE 1 ,BARBARA HALL 2 ,SYLVIE CUPFERMAN 3 ,KLAUS E. ANDERSEN 4 AND TORKIL MENNE ´ 1 1 Department of Dermatology, University Clinic Gentofte, University of Copenhagen, Copenhagen, Denmark, 2 L’Ore´al, Worldwide Safety Evaluation, River Plaza, 25-29 Quai Aulagnier, 92600 Asnie`res-sur-Seine, 3 L’Oreal, Corporate Microbiology, 188-200 rue Paul Hochart, 94550 Chevilly Larue, France, and 4 Department of Dermatology, Odense University Hospital, University of Southern Denmark, Odense, Denmark The morphology of early allergic contact dermatitis reactions was studied in formaldehyde allergic individuals exposed to a cream product preserved with 4 different concentrations of diazolidinyl urea. The study was made using a dose-escalating design in 3 different anatomical regions, the upper arm, neck and face. On the arm and neck, the dominant initial morphology was an eczematous papular eruption. In the face, the initial skin changes were more homogeneous and infiltrated erythema. Key words: diazolidinyl urea allergy; formaldehyde allergy; morphology of ROAT; ROAT. # Blackwell Munksgaard, 2006. Accepted for publication 14 August 2005 Allergic contact dermatitis (ACD) appears in sen- sitized individuals when they are exposed to the contact allergen in a dose exceeding the individual threshold level, which may also vary from one body region to another. A description of the early morphological lesions in ACD is not included in major textbooks. Based on former repeated open application test studies (ROAT) (1–3), it became clear that the early lesions are individual papules or vesicles related to the hair follicles (and maybe sweat duct orifices). As a consequence of this observation, a new scoring system was developed, which has proved useful and easy to use (4). The aim of the present study is to illustrate the early lesions of ACD in different anatomical regions as a consequence of controlled exposure to formaldehyde and diazolidinyl urea in patients with contact allergy to the respective haptens. The details of this study have been published previously (5). Patients and Methods As previously described (5), 150 eczema patients, males and females, 18–65 years of age, who pre- viously had given at least a positive patch test reaction to formaldehyde 1% aq. or diazolidinyl urea 2% petrolatum (pet.) were reviewed. 65 patients were patch tested. 10 healthy volunteers, who had given a negative patch test to formalde- hyde 1% aq. and diazolidinyl urea 2% pet., were included as controls. The formaldehyde-allergic patients were divided into 4 (non-randomised) groups of 10 and exposed to the test cream with 0.05%, 0.15%, 0.30% and 0.60% diazolidinyl urea, respectively. Additional 10 patients sensi- tized to diazolidinyl urea and some of them, simultaneously to formaldehyde (7/10), were exposed to the test cream containing 0.15% dia- zolidinyl urea. Controls were exposed to the test cream with 0.60% diazolidinyl urea. The study proceeded in a stepwise fashion with application of test cream twice daily to the 5 Â 5 cm of the healthy skin of the flexor aspect of the mid upper arm. Each anatomical area was exposed for 2 weeks. If no reaction occurred on the upper arm after 2 weeks, the cream applica- tion continued on the left side of neck for another 2 weeks, and on the face, to the whole area, except around the mouth and eyes, in a similar fashion, for further 2 weeks. Readings of the use test area were quantified according to a reading scale (6), slightly modified to also take into account any subjective reactions (7). Contact Dermatitis 2006: 54: 21–24 Copyright # Blackwell Munksgaard 2006 Printed in Singapore. All rights reserved CONTACT DERMATITIS