Coloured scanning electron micrograph (SEM) of House dust. Components such as fibre, hair, pollen, insect faecal matter and scale (animal dander) cause allergic reactions in sensitive humans. Dust in homes contains small amounts of plant pollen, human and animal hairs, textile fibres, paper fibres, insect parts, minerals from outdoor soil, human skin cell, sand many other materials which may be found in the local environment. Magnification: x26 when shortest axis printed at 25 millimetres.