The types of bacteria you share your home with are largely determined by your pets and whether your family or flatmates are mostly men or women, it has been found.
Scientists in the US and Europe took bacterial and fungal samples from 1200 homes of a wide range of styles in different climates, and compared them with equivalent samples taken outdoors.
Some types of bacteria showed up mostly in houses with pet cats; others in dog-friendly homes. Some showed a preference for man caves, others houses dominated by the fairer sex.
On the other hand, the fungi in your place depends more on where you live.
"Where you live determines what fungi live with you inside your home," the researchers write in journal Proceedings of the Royal Society B.
"By contrast, bacterial communities in indoor dust were more strongly influenced by the number and types of occupants living in the homes."
Having cats increases the presence of bacteria of the genera porphyromonas, moraxella, bacteroides, arthrobacter, blautia and neisseria, while dogs bring with them prevotella, porphyromonas, jeotgalicoccus, sporosarcina, moraxella and bifidobacterium – common in dogs' mouths and faeces.
Houses full of women attract lactobacillus, while men are more associated with dermabacter, roseburia and corynebacterium – some of which can cause diphtheria.
Previous studies have shown men shed more bacteria into their surroundings than women, explaining association with more types being found in household dust; while lactobacillus is "vaginally associated", so its presence in female-dominated households shouldn't be a surprise.
The link between the sex of a dwelling's human occupants and bacteria was weaker than that found between bacteria and pets. Computer analysis was able to predict, based on the bacteria alone, whether a home contained a dog or a cat with 92 and 83 percent accuracy, respectively.
"If you want to change the types of fungi you are exposed to in your home, then it is best to move to a different home (preferably one far away)," the researchers conclude.
"If you want to change your bacterial exposures, then you just have to change who you live with in your home."