An appliance for conditioning a liquid made of or based on milk, in particular for preparing heated liquid or a cold or heated frothed liquid. The appliance includes a tank for receiving the liquid that is to be conditioned; a closed compartment secured to the tank; and an electric device located therein for imparting a conditioning effect to the liquid. The compartment is made water impervious and washable under running water without infiltration thereof into the compartment containing the electric device.