Allergic flea dermatitis, or FAD for short, is the number one most common disease caused by fleas. Some veterinarians specializing in pet allergy claim that up to 40% of all pets can suffer from FAD. FAD is caused by an allergic reaction to one of the antigens in the saliva of fleas. There are 13 different antigens that have been identified in flea saliva and if your pet is sensitive to even one of them it could have an allergic reaction and develop FAD.
Because there are different flea species even if your pet has never had an allergy before when you move to a new state or even a new city if there are different flea species in that area your pet may show signs of FAD. FAD is often aggravated by seasonal allergies that usually occur in summer and autumn.
The symptoms of FAD are general and can make it difficult to understand if your pet is reacting to a bite or if he has a general allergy to something in his environment. The most obvious symptom of FAD is hair loss and general itching, especially above pets and near the tail. As the animal feels itchy, it may begin to overhang. Excessive care can cause a completely different set of problems, including secondary skin infections, hair loss and skin lesions.
Often pets who have FAD will develop “hot spots” which are areas that seem more itchy than others and areas where your pet overly licks and pulls his fur. Particularly sensitive cats can even develop a disorder called feline eosinophilic granuloma which can be very serious and can cause injury and inflammation inside the mouth.