Abstract: A throughflow heater comprises an outer surface encircling a longitudinal axis, inwardly adjoining the outer surface a conveying region for a fluid that is to be heated, inwardly adjoining the conveying region at a transition surface a heating layer with an electrical heating element and heat-conducting material, and an insulating core which extends centrally along the longitudinal axis and outwardly forms a support surface for the electrical heating element and the heat-conducting material. The thermal conductivity of the insulating core is lower than that of the heat-conducting material. The radial extent of a channel arranged in the conveying region is less than 1 mm.