Dog and cat allergens are found in almost every home in the United States, whether or not dogs and cats live there! In homes with dogs and cats, the level of allergens are almost always high enough they can trigger allergies or asthma. But even many homes without dogs or cats have dander levels high enough to provoke allergy symptoms.
Where does this come from? Presumable it is dragged into homes on clothes and rubs off where people commonly sit. It also gets into the air. High efficiency particulate air filtering (HEPA) systems in air purifiers and vacuums can help reduce exposure levels.
Make sure you are always using a vacuum with a HEPA filter like the cleaners at www.maidsway.com do.