The handpiece for treating the skin with irradiation using a light beam (F1), comprises a first window (1) and a second window (2) and first means for cooling the first window (1). Said first window (1) and said second window (2) are positioned opposite one another and are separated by a gas-filled space. They are capable of transmitting a light beam (F1) and said first window (1) is intended to be applied in contact with the skin during the treatment. The handpiece comprises means for heating the gas between the two windows (1, 2).
