In fact, cat hair itself does not cause allergies. The reason cats cause allergies in humans is a tiny protein called an allergen. It exists in the fat glands of cats. This substance is emitted through sebum and adheres to dry skin, which is our common dander. Allergens can also be present in the saliva and urine of moving cats and can be spread through the air when cats lick their coat. Allergy to cat fur can cause symptoms such as sneezing, runny nose, itchy and swollen eyes, and spots on the skin.