What are the specks observed falling from a pet after scratching primarily composed of?

The specks observed falling from a pet after scratching are primarily composed of fecal blood, particularly if the pet has fleas. Flea feces, often referred to as "flea dirt," consists of digested blood excreted by the fleas after feeding on the pet's blood. When a pet scratches, these specks can be dislodged from their fur and appear to fall to the ground.

Understanding this is crucial for pet owners as it highlights the potential presence of fleas and other parasites, indicating that the pet may require treatment. In contrast, while skin cells, dust, dirt, and pet hair can also be found in a pet's environment, they do not specifically correlate to the characteristic specks seen after scratching as strongly as flea feces does.