A delivery device (1) for the sequential delivery of at least two substances for example and antibiotic and sealant for treating dairy cow teats is disclosed. The device includes a body (2), a plunger (3) and a partition (5) defining a first chamber (6) in front of the partition and a second chamber (7) behind the partition. The partition (5) includes a conduit (8) for passage of a substance from the second chamber (7) to the first chamber (6). The partition (5) includes a deformable component in the form of a hinged flap (9) that engages with the conduit in a closed position to prevent passage of a substance between chambers. When the hinged flap (9) is opened, for example by pressure in the second chamber (7), the substance in the second chamber (7) can be ejected through the first chamber (6) to an outlet (4).
