The present invention provides a mask for delivery of an aerosolized or nebulized drug to a patient. The mask has an inner surface configured to generate a helical flow of gases within the inner space between the mask and the patient's face after the gases rebound from the patient's face during the process of gas delivery through the mask. The helical flow of gases minimizes the leakage of gases from the interior of said mask under the rim of the mask and toward the patient's eyes.
