Methods: 36 patients with metastatic colorectal cancer or metastatic head and neck cancer allocated to treatment with chemotherapy and biweekly cetuximab. Two equally sized areas of at least 10x10 cm on the back or chest of the patient is marked. Patients receive in a double blinded procedure placebo lotion on one side and vitamin K3 lotion on the other side. The treatment may last for a maximum of two months and the patients are followed biweekly with photos, VAS-scores, questionnaires and CTCAE estimations. The patient will be able to take weekly photos at home during the weeks they are not seen at the outpatient clinic. During the treatment all other skin products or antibiotics is allowed and will be carefully registered by the health care professionals in the outpatient clinic.