An elastomeric or polymeric seal assembly (10) includes an annular elastomeric or polymeric sealing element (60), an internal circumferential surface of which sealingly engaging a first component (12), the sealing element abutting a radial annular face of a second component (16) and an external circumferential surface of the sealing element sealingly engaging an internal circumferential surface of a second component, a vent (92) being provided in the internal circumferential surface of the second component adjacent to the radial face, to vent the space between the external circumferential surface of the sealing element and the internal circumferential surface of the second component, an inlet to the vent being defined by an annular groove (88) in the internal circumferential surface of the second component, an annular helically wound element (94) being provided in the annular groove to prevent extrusion of the sealing element into the vent, the helically wound element being formed from a strip of material of elongate section, adjacent winds of material being spaced from one another.