Some people start sneezing or get a runny nose when they’re around certain animals, like cats or dogs. Many then say that they’re allergic to the animal’s fur. But it isn’t the fur that triggers an allergic reaction. Instead, it’s proteins that are found in the animal’s dander (flakes of skin), sweat, skin oil, saliva (spit), urine and feces ("poop").
These allergy triggers (allergens) stick to the animal’s fur and end up on objects like carpets or soft furniture. But particles with the protein on them also float through the air and spread in that way. The allergens enter the body if you breathe them in or they come into contact with your skin.