One of the most telling symptoms of a flea bite is the appearance of a small, raised reddish spot on the skin with a small puncture mark in the center. The bite might cause itching, and bleeding can result from constant scratching. If an individual is allergic to flea bites, hives can develop in the surrounding area. Flea bites usually appear in multiples, and often occur around ankles, legs, and along other joints in the body. Although symptoms of a flea bite are generally similar between humans and animals, pets can exhibit several other signs, such as bald patches of fur.

Fleas feed primarily on blood, and eat by biting into the skin and sucking. The pressure causes the skin to rise, creating a small bump. The puncture wound is usually large enough to be seen by the naked eye and is usually spotted as a small red-black scab in the center of the bump. The red coloration of a flea bite is due to both the damage to the skin and irritation caused by the flea's saliva. Fleas usually feed on multiple areas of the body, resulting in a rash-like appearance to the bites.

Flea saliva can be a powerful irritant, and is usually the cause of the more distressing symptoms of a flea bite. The bites can be very itchy, and scratching the tender skin can result in more damage. It is not uncommon for wounds to break on scratched bites; depending on the individual, these wounds can eventually result in scars. People allergic to flea saliva can also develop hives, which are exhibited as blotchy red patches of skin. The hives themselves can be inflamed and cause additional itching.

The symptoms of a flea bite usually appear in the lower parts of the human body, as these are the areas that are most accessible to fleas carried by pets. Depending on the number and level of activity of the fleas, bites can run the entire length on the leg. It is also possible for fleas to find their ways to higher areas of the body, particularly if an individual is fond of carrying his pet.

Flea bites on a pet are usually harder to spot, as the bites tend to be covered by fur. Tell-tale symptoms of a flea bite on pets include frequent scratching, small amounts of blood on the animal's fur, and bald spots where the scratching is most vigorous. The skin around a flea bite might be more sensitive, causing pets to jerk when touched in bitten areas.