According to the American College of Allergy, Asthma & Immunology (ACAAI), almost 10% of the total U.S. population are allergic to animals (Pet Allergy). Dander is material shed from the body of various animals, similar to dandruff or pet pollen. It may contain scales of dried skin and hair. It's often thought that people who are sensitive to dogs are reacting to the dog hair. While shedding (see moult) can contribute to allergies, often people are sensitive to substances in the the dander (dead skin cells) and saliva. The very small, sticky, and lightweight saliva and dander allergens float about in the air and around the home, contaminating almost everything it comes into contact with.