MICROSCOPIC DINERS
Within the bundles of dust gathering on bookcases and hidden behind sofas are microscopic organisms called dust mites. Around a third of a millimetre in size, these tiny mites are well adapted to life among household dirt and feed on the many flakes of human skin within. Although they look like insects, they are eight-legged arthropods, making them more closely related to spiders. Though typically harmless, the dead bodies of the mites and the waste that they produce after a skin cell meal can cause allergic reactions among some people. Symptoms are comparable to those experienced by hay fever sufferers, such as sneezing, a runny nose and postnasal drip.