Fleas consume your pet's blood and can be dangerous to their and your health,
so you need to be able to recognize the signs your cat has fleas. Reaction to
fleas by cats can sometimes be overlooked as regular grooming, especially when
your cat has first caught fleas. 
But as time goes on, the incessant
scratching, biting its coat, or showing other signs of discomfort will point to
a more serious problem. On cats,
fleas generally affect cats on the face, neck and back. Another signs
your cat had fleas is feeling small bumps on the skin when you pet them.
Other signs your cat has fleas include seeing the fleas after combing the cat with a fine metal comb. If the infestation is heavy, then you might be able to see the fleas climbing on the comb. For light infestations, you can comb your cat over a white sheet of paper, flea feces, which is dried blood, will accumulate on the paper along with any loose hair. After removing the hair, place the dirt and possible feces onto a damp cloth. If flea feces are present they will dissolve and leave a light red spot.
A normal cat, even with a few dozen fleas, will only react with a little
itching/scratching. Flea bites can cause an allergic reaction called flea
allergy dermatitis in cats that are susceptible to the flea’s saliva.
In fact, flea allergy is the most common allergy in cats and sensitivity to flea
bites increases as a cat gets older. The worst time of year for fleas is May
through September or year round in warmer climates. A sign your cat has fleas
and is allergic to the flea’s saliva is by the amount of intense itching with
scratching, chewing and licking especially near the rump and back legs. 
Flea
allergy dermatitis can lead to permanent hair loss and other skin problems (open
sores and scabs with the possibility of secondary skin infections requiring
antibiotics) due to the scratching by the cat to rid itself from the fleas. Some
cats can be desensitized to flea saliva over a prolonged period of time through
the use of
corticosteroids, which can also be used to control the allergy
reactions.
If a pet is overwhelmed with fleas, they can suffer from anemia due to the loss of blood. Fleas can also carry other parasites from sources previously bitten including tapeworms. Fortunately, ridding your cat of fleas is easier today than in the past and prevention is even easier. Recognizing the signs your cat has fleas is necessary to maintain a healthy and happy feline companion.
