Dermal delivery device with in situ seal

This invention relates to a transdermal drug delivery device that comprises an active ingredient (Al) layer, having a skin contacting surface and a non-skin contacting surface and comprising a volatile component, a release liner impermeable to the volatile component adjacent the skin contacting surface of the Al layer having a pe meter that extends beyond the perimeter of the Al layer in all directions, and an overlay comp sing a pressure sensitive adhesive (PSA) that does not absorb the volatile component adjacent the non-skin contacting surface of the Al layer having a pe meter of which extends beyond the penmeter of the Al layer in all directions, wherein the release liner and the PSA of the overlay are in contact with and adhered to each other around the pe meter of the Al layer to form a seal that reduces or prevents volatile component loss.