Abstract: An apparatus is disclosed for detecting moisture, which is intended for the use in an apparatus for monitoring an access to a patient for a device by means of which a fluid is conducted to and/or removed from a patient via a hose line, in particular for monitoring the vascular access during an extracorporeal blood treatment, wherein blood of a patient is removed from the patient via an arterial hose line, which has an arterial puncture cannula, and is conducted back to the patient via a venous hose line, which has a venous puncture cannula. The apparatus for detecting moisture is designed as a pad which is made of a flexible material and is to be applied onto the patient's skin and which comprises an upper side facing away from the patient's skin and a lower side facing the patient's skin. The pad comprises an opening for the passage of fluid, in particular blood, and a moisture sensor having contact elements for the connection of the same.