The invention refers to a device for and a method of detecting a disease of the udder of an animal. The device comprises means (9) for appreciating a parameter related to the quantity of milk extracted from a first and at least a second teat of said animal during at least one milking operation. Means (6) is arranged to determine a deviation of said parameter from a comparison value, and means (7) is arranged to display said deviation as an indication of an inflammation of the first teat in the case that said deviation exceeds a certain level. The determining means is arranged to define said comparison value by including the level of said parameter regarding said second teat during said milking operation.