A dressing composition for use as a skin dressing comprises an elastomeric-adhesive composition, and a zeolite comprising releasably adsorbed nitric oxide. The zeolite may comprise a transition metal cation such as Co, Fe, Mn, Ni, Cu, Zn, Ag or a mixture thereof as an extra-framework metal cation, preferably Zn. The elastomeric adhesive composition may be a hydrocolloid-adhesive composition comprising, hydrocolloid and elastomer. The dressing composition releases nitric oxide, which may have beneficial effects, when used on wounds or moist skin, with a substantially constant release rate over a long period of time. A dressing including a layer of the dressing composition has a backing layer and may have a release liner removably attached to the skin-contacting surface of the dressing layer.