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 The dust that accumulates in the corners of your house does more than cause allergies¹ and aggravations. It's also teeming² with clues about where you live and who you live with. That's the finding of  a study in the Proceedings³ of Royal Society B. Researchers had volunteers at nearly twelve hundred homes across the US collect indoor and outdoor dust samples. The average home dust contains about fivethousand types of bacteria and two thousand types of fungi⁴. The fungi gave away a lot about home's  location. Different regions have different fungi populations, and thus so do  houses within those regions. For example, dwellings⁵ around the Great Lakes had very different fungi than  its homes at Arizona, because most household fungi originate outside and common either on people's clothes or through windows and doors. As for the bacteria, those are the strong indicators⁶ of the identity of the homes' residents. Much of the bacteria were shed by the human body and was a pretty good indicator⁷ of a home's gender⁸ ratio. The single-celled organisms also showed whether a pet shared the home. Cats and dogs make their own contributions to indoor bacteria ? The research couldn't form forensic⁹ investigations¹⁰ and allergy¹¹ studies. In the mean time what can we take from these findings? Well you can clean up dust but you can't change its composition, that is , unless you move or make some changes in the pets and people you live with.