Final answer:
Flea allergic dermatitis primarily affects cats and dogs, causing an allergic reaction to flea bites that is different from allergic conditions such as eczema in humans.
Step-by-step explanation:
The animals commonly affected by Flea allergic dermatitis are cats and dogs. This condition is an allergic reaction to flea bites, where the saliva of the flea causes an intense allergic response in the affected animal. Unlike humans, who may suffer from eczema or other allergic reactions such as cat-scratch disease from Bartonella henselae, cats and dogs have a more direct reaction to the presence of fleas themselves. Birds and reptiles are not commonly affected by this condition.