What is flea allergy dermatitis?
Flea allergy dermatitis (FAD) is a skin condition caused by an allergic reaction to the proteins in flea saliva. In an allergic reaction, the body’s immune system overreacts or is hypersensitive to a substance (antigen) that is usually harmless.
When a flea bites a cat to consume a blood meal, some of its saliva is injected into the skin. Cats usually experience only minor skin irritation in response to flea bites. However, in a cat with flea allergies, the antigens in flea saliva cause an intensely itchy response. Fleas are often difficult to find because cats groom them away, but the allergic reaction can continue long after the bite has occurred.
Cats with FAD do not have to be infested with fleas to be itchy: a single flea bite can cause itching for several days. Fleas typically only stay on the cat for the minutes to hours they feed, which is why you do not often see live fleas on your cat unless there is a severe flea infestation in their immediate environment.
Are only certain cats allergic to fleas?
FAD can develop at any age. Cats with other types of allergies, such as environmental allergies (e.g., pollen, molds, dust mites) tend to be highly sensitive to flea bites and are much more susceptible to FAD than other cats.
What are the clinical signs of FAD?
Signs of FAD in cats include:
- Itching and hair loss around the tail base, neck, and head.
- Chewing, licking, and hair loss on the legs.
- Numerous small scabs around the head and neck, often called miliary dermatitis because the scabs look like millet seeds.
- Scabs, sores, or skin infections due to scratching.
How is FAD diagnosed?
Clinical signs often indicate that your cat suffers from FAD. Cats are such thorough groomers that it is frequently impossible to find any evidence of fleas or flea dirt on the coat, especially if only one or two fleas are causing the problem. Intradermal allergy tests (skin tests like those performed in humans) or specialized blood tests (IgE blood tests) can confirm a flea allergy in your cat.
How is FAD treated?
Strict flea control is essential in treating FAD, because the injection of flea saliva causes an allergic response. Even if you do not see fleas on your cat, it is important to continue rigorous flea treatment and maintain environmental control. Most flea infestations occur in warmer weather but can happen year-round.
The best treatment is flea prevention, using modern oral or topical medications. Speak to your veterinarian about the best option for preventative treatment for fleas, as there are many choices available.
Can FAD be treated with desensitization?
Desensitization involves giving your pet a series of increasing doses of a diluted flea antigen over a prolonged period. Sometimes, these allergy injections may be required for life. Unfortunately, desensitization is not considered a successful treatment for FAD in cats and is rarely used. However, do not confuse desensitization therapy with corticosteroid or cortisone injections, which relieve the symptoms of an acute FAD flare-up.
Can FAD be treated with steroids or other drugs?
Corticosteroids are widely used to treat acute (sudden) episodes of FAD and provide immediate relief from intense itching. Corticosteroids are often necessary for treating the condition, especially during the initial stages. Steroid use has significant potential side effects, although cats are more resistant to the side effects than humans and dogs. For this reason, the goal is to use the lowest dose of corticosteroid possible to keep the cat comfortable. Prednisolone is commonly used for short-term relief while flea control is implemented. The goal is to use the lowest dose of corticosteroids possible, weaning down to alternating days or every three days.
Oclacitinib (Apoquel®) has been tried in cats as a non-corticosteroid alternative for this condition, but its use is off label, and more research is required. Antibiotics may be necessary if your cat develops a secondary bacterial skin infection due to scratching. Occasionally, topical treatments with shampoos and sprays may be considered.
Your veterinarian will discuss the advantages and disadvantages of the various treatments for FAD during the examination and will recommend the safest and most effective treatment for your pet's needs. Prevention is essential, simple, and inexpensive.
