A 63-year-old woman with a metastatic colorectal cancer presented with a 5-day history of an erythematous itching vesicular eruption on photo-exposed areas of the face (Figure 1). During the previous 12 months the patient underwent 13 intravenous chemotherapy cycles with cetuximab 375 mg in combination with irinotecan 270 mg, fluorouracile (5FU) 600 mg, and folic acid 150 mg every 2 weeks, with no reported adverse drug reactions. Dermatitis developed during the last cycle of chemotherapy and after the application of a skin cream containing 0.1% vitamin K 1 (VigorSkinK1, Merck Serono, Italy). The patient was exposed to the sun during her daily outdoor activities and 10 days after the application of the vitamin K 1 cream the photo-induced reaction commenced. Patch tests with the SIDAPA (Società Italiana di Dermatologia Allergologica Professionale ed Ambientale) baseline and cosmetic series (Firma Diagent, Florence, Italy) were applied to the back with Finn Chambers (SmartPractice, Phoenix, Arizona) on Scanpor tape (Norgesplaster, Vennesla, Norway) and readings were taken on day (D) 2, D4, and D7. All patch tests were negative. Photopatch tests were performed with the standard SIDAPA photopatch series (Euromedical, Calolziocorte Lecco, Italy), the commercial cream VigorSkinK 1 "as is", and Konakion (aqueous solution 1 mg/mL, Cheplapharm Arzneimittel, Mesekenhagen, Germany).The allergens on the left side of the back were covered with an ultraviolet (UV) radiation-opaque material, and those on the right side were irradiated with 4 J/cm 2 UVA light (Waldmann UV, 801 KL Phototherapy, Herbert Waldmann, Villingen-Schwenningen, Germany). Readings were performed on D2, D4, and D7 according to ESCD guidelines.