Household dust. Coloured Scanning Electron Micro- graph (SEM) of a sample of household dust. Dust contains an assortment of substances which can cause asthma or other allergic reactions. The allergens seen here include: long hairs such as cat fur, twisted synthetic and woollen fibres, serrated insect scales, a pollen grain, plant and insect remains. Asthma or hay fever are often a hypersensitive and irritant response to substances that, in most people, are harmless. Airborne allergens may come into contact with the respiratory airways, skin or surface of the eye. Magnification: x115 at 6x7cm size. x380 at 8x12"~LANDSCAPE"