Parasites are "freeloaders" that live in or on another creature. Fleas are the most common external parasite found on dogs and cats. Although fleas are more likely to be a problem during warm-weather months, they can also cause problems during cooler seasons due to their ability to continue their life cycle indoors.
How will fleas affect a dog?
You will probably first notice the effects of fleas when a dog repeatedly scratches and chews its coat. You may see fleas or flea dirt on your dog. A dog's constant scratching may lead to visible patches of hair loss and reddened, irritated skin. Fleas can also transmit other parasites, such as tapeworms, to a dog.
How will fleas affect a cat?
You may first notice the effects of fleas when a cat repeatedly nibbles at, and licks, its coat and skin. You may see fleas or flea dirt on your cat. Cats are very skilled groomers, however, and may remove fleas so well that you do not see them. A cat's constant nibbling and licking may lead to noticeable patches of hair loss, tiny crusts (called miliary dermatitis) and reddened, irritated skin. Fleas may also transmit other parasites, such as tapeworms, to a cat.