Household pets are the main culprits in causing allergic reactions to animals. It was once thought that pet allergy was provoked by dander or fur from cats and dogs. Now, however, the allergen is known to be proteins in the saliva that is present on the dander or fur.
Cats win the prize for causing the most allergic reactions.
One reason may be that cats preen themselves more than other furry pets. This preening coats the hairs with saliva containing allergens, which become airborne when the saliva dries. Also, it may be because cats are held more and often spend more time in the house, close to humans, than do dogs. Some rodents, such as guinea pigs and gerbils, have become increasingly popular as household pets. They, too, can cause allergic reactions in some people.