Though it can be an allergenic food, many people are usually allergic to the protein in the white and can continue to eat the yolk with impunity! (caitliniles.ca)
It should be noted that some have said that fish is allergenic in cats. (cat-lovers-only.com)
According to Dr. Mahaney, flea bite saliva can also be allergenic for some dogs and cats. (laurelwoodvets.com)