A cosmetic method for treating the scalp to slow and prevent hair loss, which consists in: - performing, during a first step, a mechanical massage with suction of at least one portion of the surface of the scalp; - arranging, during a second step, on the at least one portion of the surface of the scalp, a mixture which comprises, in proportions which can vary from 0,01% to 30%, a chemical compound for use as a cosmetic product having the formula C 9 H 15 N 5 O; - subjecting, during a step, the at least one portion of the surface of the scalp to the luminous radiation emitted by a plurality of light-emitting diodes; the mechanical massage with suction performed during said first step consisting in arranging on the portion of the surface to be treated of the scalp a suction inlet, which is adapted to determine a partial vacuum on the skin that faces said inlet and is delimited thereby; said suction inlet comprising massaging means which subject to a mechanical treatment the portion of surface to be treated of the scalp that faces said inlet and is proximate thereto; said suction inlet being movable by an operator along the surface of the scalp; said diodes being suitable to subject the scalp of a patient, wearing a helmet provided on its internal surface with said diodes, to luminous biostimulation at a wavelength and emission power adapted to enable enhanced absorption of the mixture in the scalp; said biostimulating radiation comprising at least one among the following light beams: a red light beam to stimulate collagen production, a blue light beam to contrast bacterial actions, a yellow light beam to stimulate the lymphatic system and the nervous system; said diodes being all arranged at the same distance from the portion of the surface to be treated, said distance being calculated as a function of the characteristics of the intensity and frequency of the beam emitted by the particular type of diode. - performing, during a first step, a mechanical massage with suction of at least one portion of the surface of the scalp; - arranging, during a second step, on the at least one portion of the surface of the scalp, a mixture which comprises, in proportions which can vary from 0,01% to 30%, a chemical compound for use as a cosmetic product having the formula C 9 H 15 N 5 O; - subjecting, during a step, the at least one portion of the surface of the scalp to the luminous radiation emitted by a plurality of light-emitting diodes; the mechanical massage with suction performed during said first step consisting in arranging on the portion of the surface to be treated of the scalp a suction inlet, which is adapted to determine a partial vacuum on the skin that faces said inlet and is delimited thereby; said suction inlet comprising massaging means which subject to a mechanical treatment the portion of surface to be treated of the scalp that faces said inlet and is proximate thereto; said suction inlet being movable by an operator along the surface of the scalp; said diodes being suitable to subject the scalp of a patient, wearing a helmet provided on its internal surface with said diodes, to luminous biostimulation at a wavelength and emission power adapted to enable enhanced absorption of the mixture in the scalp; said biostimulating radiation comprising at least one among the following light beams: a red light beam to stimulate collagen production, a blue light beam to contrast bacterial actions, a yellow light beam to stimulate the lymphatic system and the nervous system; said diodes being all arranged at the same distance from the portion of the surface to be treated, said distance being calculated as a function of the characteristics of the intensity and frequency of the beam emitted by the particular type of diode.