Fullerton A, Avnstorp C, Agner T, Dahl JC, Olsen LO, Serup J
DOI: 10.2340/0001555576194202

One hundred and sixty-eight individuals (psoriatic patients treated with calcipotriol with dermatitis due to calcipotriol, psoriatic patients treated with calcipotriol with no dermatitis, psoriatic patients never treated with calcipotriol, patients with eczema and healthy volunteers) were patch-tested (Finn chambers, back, 48 h) with dilutions of calcipotriol ointment (50, 10, 2, 0.4 micrograms/g) and an ointment vehicle. Test evaluation was based on clinical scoring and various non-invasive measuring methods. Doubtful (?+) and weak (1+) reactions were common, irrespective of patient group and history. Moderate (2+) reactions were uncommon and with no increased frequency among psoriatic patients with adverse dermatitis during calcipotriol treatment. The blood flow of test sites measured by laser Doppler flowmetry was, however, increased in psoriatics, who developed dermatitis during calcipotriol treatment as an isolated finding. Furthermore a 1-week repeated open application test (ROAT) was performed on all subjects. None of the persons having a strong reaction in the patch test showed any dermatitis in the ROAT test, indicating that they were not sensitized. Calcipotriol was found to be a mild irritant of the non-corrosive type, i.e. with no influence on the skin barrier. Reactions were dominated by redness (increased laser Doppler flow and chroma a*) and only oedema formation in advanced reactions. The calcipotriol dose-irritation curve was found to be scattered. Calcipotriol induced no increase of transepidermal water loss (TEWL) versus the ointment vehicle, but the ointment vehicle itself increased TEWL. The special ointment vehicle needed for calcipotriol for stability reasons may itself be irritant and cause some impairment of the skin water barrier, with increase in TEWL values. Future patch test studies for calcipotriol allergy should not be done with this vehicle. The non-irritant threshold concentration of calcipotriol in an appropriate test vehicle is still unknown.