Flea allergic dermatitis (FAD) is one of the most common hypersensitivity (allergic) reactions in cats. It is caused by the cat’s immune system over-reacting to the proteins or antigens in the saliva of a flea. When a flea bites, some of its saliva is injected into the cat’s skin to cause an allergic response. The cat will develop intense itching and a rash/scabs every time they are bitten.

Most cats will experience only minor irritation to flea bites and even when dozens of fleas are present, there will be minimal itching. In contrast, a cat with a flea allergy will have a substantial reaction to even a single flea bite. Even one bite can cause severe itching that lasts for days – they do not have to be infested with fleas.

The intense itching caused by the flea bites will lead a cat to chew, lick, scratch and over-groom. This can lead to hair loss and numerous small bumpy scabs on the skin which almost feel like grit under the fur; a pattern known as military dermatitis. This usually occurs over the rump and the back of the cat but may also affect the neck and cheeks. Furthermore, cats may over-groom and cause hair loss to the tail-base and legs, and this can progress to red, raw patches of skin.

This over-grooming can mean that as an owner or vet, you may never actually see a flea. It is often impossible to find evidence of flea dirt or the fleas themselves as they are rapidly groomed out by the cat, and there may only be one or two fleas anyway.

Diagnosis is often based on clinical presumption and history; however, the allergy can be confirmed using intradermal allergy tests or specialised blood tests.

Left untreated, a cat’s quality of life can be severely affected by FAD. The mainstay and most important treatment for FAD is to remove the fleas. This is achieved with prescription flea treatments at strict intervals for the lifetime of the cat. All animals in the house need to be treated otherwise rogue fleas can jump back on to the allergic cat and bite; remember just one bite can cause a severe reaction. The house itself may also need to be treated with a household flea spray and thoroughly cleaned/vacuumed. Only 5% of a flea infestation lives on your pet, the rest live in your home.

If a cat is severely affected, corticosteroids (steroids) may be used to give immediate relief through blocking the allergic reaction, however this is purely symptomatic treatment and will not remove the allergy or treat the fleas. Occasionally, antibiotics are required if the skin has become infected through the trauma of being scratched, and it may be necessary to use a buster collar or body suit to prevent self-trauma.

If you are concerned about FAD in your cat, contact the practice on 01626 835 002 to arrange a veterinary consultation. Our pet health plan can prove invaluable for such conditions with the flea treatments delivered direct to your door.