Stains on a ceiling or a wall can often be caused by dampness. First, the source of the dampness must be traced and eliminated.
With ceilings always check the loft. Once the dampness is cured and the ceiling has dried out remove any damaged paper, if necessary. Then seal the stains with two coats of aluminium sealer. Allow the sealer to dry. Then repaint or repaper the area.
Follow the same procedure with walls. Points to check include the damp course and external air bricks. Once the source of damp has been removed, seal the walls-inside and out – with sealer before repainting. If the trouble persists. However, always call in a professional for advice.