Sebaceous glands are small glands that are attached to the hair follicles under the skin. SH occurs when they become enlarged and trapped with sebum (skin oil). This creates shiny bumps on the skin, mostly the forehead or nose, that are harmless but cosmetically unacceptable for some. SH causes painless yellow or flesh-coloured bumps measuring 2-4mm in width.
People that are most at risk are middle aged or older who have a fair skin and have had a lot of sun exposure. There could also be a genetic component and in very rare cases is linked to Muir-Torre syndrome.
People taking immunosuppressant medication eg. cyclosporine are also much more likely to develop SH.
Although a small number of cases can be cured a more realistic expectation would be to significantly improve cosmesis using any of the above treatments. Most cases will require maintenance therapy in the long term.