The Protein, Not the Fur
Fel d 1 is a small, unusually stable glycoprotein secreted primarily in a cat's sebaceous glands, salivary glands, and anal glands. When a cat grooms itself, saliva loaded with Fel d 1 coats every strand of fur. As that saliva dries, it breaks into microscopic particles light enough to stay airborne for hours. Those particles land on upholstery, bedding, clothing, and the inside of your nose, which is where the immune system reads them as a threat and launches the histamine response you experience as sneezing, itching, and watering eyes.
