An animal mask for removable fitment to the appropriate portion of the head of an animal such as the front of the head or over one nostril for the effective delivery of drugs or medicaments, for pulmonary or nasal absorption. The rings of the mask are nestable, forming a succession of monotonically decreasing sized telescopable rings from a largest ring to a smallest ring to form a relatively flexible skirt. An animal interface adapter extends from the largest ring and is adapted to establish a substantial seal between the animal interface adapter and the face of an animal. The animal mask is collapsible to permit use in a full or partially open state, and to permit easy and convenient transport in a collapsed or closed state.