The most telltale sign of a flea infestation is the sight of your cat or dog incessantly scratching himself due to the itching and misery that fleas cause, but an infestation is not always so easy to spot and other methods of detection must be used.
If you have pets, this is where a flea comb can come in handy because it has fine blades that can filter out adult fleas, flea eggs, and flea dirt that are hidden or may be matted in the hair of the animal.
Flea dirt is the feces and dried blood left behind by adult fleas, and it looks like tiny brown or black specks similar to coffee grounds. It may be scattered about on the floor especially in the places where your pets sleep or travel frequently. If you find flea dirt, then that is a definite sign of a flea infestation.
Keep in mind that the immature stages of the flea life cycle such as flea eggs and flea larvae are difficult to see with the naked eye.
The flea larva weave cocoons and can lay dormant for several months waiting for a host to come by, and will come out of the dormancy when they detect movement, so even though you can’t see them you may still have an infestation.