Silverfish eat starch: book bindings, wallpaper paste, cardboard boxes, photographs, cotton and linen left in storage. They want dark, humid and undisturbed, which is why they turn up in the linen press, the back of the wardrobe, under the bathroom vanity and through the roof void. Damage shows as ragged holes and grazed patches on paper, plus yellow staining and shed skins. They breed slowly, so by the time anyone notices, it has been building for a fair while.
Dust is the right tool here. It goes into wall cavities, the roof void, behind architraves and skirtings and into the wardrobe frame, where it stays put and keeps working for months. A liquid spray wiped across a shelf wears off fast and never reaches them anyway. Weatherboard homes around Herne Hill and Newtown with older insulation get them worst. Dropping the humidity helps as much as the treatment does: vent the bathroom properly, get boxes up off the floor, and move stored linen out of cardboard and into sealed tubs.