There is no definitive answer when it comes to the most hypoallergenic cat. However, there are certain breeds that are known to produce less of the Fel d 1 protein, which is what causes allergies in people. Some of these breeds include the Sphynx, Devon Rex, Cornish Rex and Peterbald. Other factors that can affect how allergic someone is to a particular cat includes whether or not the cat licks itself (which spreads the allergen around), how much time the person spends around the cat and if the person has any other allergies.