The present invention relates to an applicator for applying a cosmetic composition to human keratinous materials, the applicator comprising: a base including a reception zone and an electric heater element having two opposite sides; and an applicator unit comprising a support that extends along a longitudinal axis, that is fastened in removable manner on the reception zone, and that carries a mass of cosmetic composition that presents an application face that is suitable for coming into contact with keratinous materials; the mass of composition having a greatest dimension that is less than 40 mm, extending on only one side of the electric heater element, and being carried by the support before fastening the unit on the base.