All cats can potentially trigger an allergic reaction regardless of the length of their hair. The most common allergen in cats is a protein called Fel d 1. The protein is mainly found in secretions from by the sebaceous and salivary glands. As the cat grooms itself its skin and fur becomes coated in this protein. As cats are constantly shedding minute flakes of skin (called dander) the Fel d1 protein becomes airborne and triggers the human allergenic response.