Having dogs and cats in the house is like living in a kennel. Some people that have carpet in their house even have dogs and cats. Can you imagine how filthy that carpet must be?!
Don't image, have a look. At a glance your carpet may look clean but under a microscope its a whole different story. This is pet dander in carpet.
And this is just one of the little critters that feast on pet dander in carpet.
Dinner is served! This may look like a dog scratching but it is really a dog preparing another meal for the bugs in your carpet.
Humans shed skin and hair, and feed the mites too.
Having a pet of course increases this, but unless you live in a sealed bubble, your house is going to be full of dirt and bugs no matter what.