A housing is secured to an area of skin to allow suction to be applied to a local area of skin through an aperture. After formation of a suction blister, a blade is actuated to sever a suction cup thereby detaching the means for creating suction at the aperture and at the same time removing the roof of the suction blister to expose an area of dermis from which the skin's epidermis has been removed. A rotatable portion of the apparatus is then moved into a position in which a port communicates with a compartment within the rotatable portion. The compartment may contain a reservoir of fluid substance to be transdermally absorbed or may contain means for taking a sample of exudate produced at the exposed dermis. A modified apparatus has means for applying suction to the exposed dermis to enhance the rate at which exudate is formed and for handling a sample of exudate for analysis. Transdermal delivery and sampling are thereby achieved non-invasively and without the impediment of the skin's epidermis.