Fleas can no doubt be a nuisance, causing itching and allergic reactions. What most people don't know, however, is that fleas can actually be life threatening. Flea anemia can occur when a pet is infested with a large amount of fleas that go mostly undetected so that the fleas drink so much blood that the animal becomes anemic. The blood loss weakens the pet and eventually catches up to him, which can lead to death. Flea anemia is actually more common that one would think. It's fairly easy for fleas to go unnoticed since only pets allergic to fleas scratch or experience hair loss. Animals that are not allergic may show no signs of flea infestation.

Certain pets are at a greater risk for flea anemia, including young kittens raised outdoors or with an outdoor mother cat, elderly outdoor cats, and outdoor puppies. One of the most common signs of anemia is pale gums. Pets may be listless and cold in serious cases, and anemic cats may eat litter or small pebbles. Veterinarians can assess the degree of anemia with a hematocrit or packed cell volume (PCV) test. Serious cases may require blood transfusions or transfusion with blood substitutes. The fleas must also be removed from the pet and his environment, which can be problematic for critically ill pets as they may be too sick for baths or flea control products.