How do fleas bite people? - briefly
Fleas use needle‑like mouthparts to pierce the skin and inject saliva that contains anticoagulants, allowing them to feed on blood. The result is a tiny, red, itchy spot that may appear in a group of closely spaced bites.
How do fleas bite people? - in detail
Fleas attach to human skin using their powerful hind legs, which enable a rapid jump onto a host and a firm grasp on hair or clothing fibers. Their mouthparts consist of a piercing‑sucking stylet composed of two elongated mandibles that cut the epidermis and two shorter maxillae that form a canal for fluid intake. When the flea lands on a person, it inserts the stylet at an angle of approximately 30–45 degrees, penetrating the superficial layers of the epidermis and reaching the capillary network in the dermis.
Saliva is introduced simultaneously with the puncture. The fluid contains anticoagulants, such as apyrase, which inhibit platelet aggregation and prevent blood clotting, and anesthetic compounds that reduce the host’s immediate sensation of the bite. This combination allows the flea to feed uninterrupted for several minutes, ingesting small volumes of blood (typically 0.5–1 µL per feeding episode).
During the feeding process, the flea’s foregut contracts rhythmically, drawing blood upward through the maxillary canal. The ingested blood is stored in the midgut, where it is digested and metabolized. After feeding, the flea withdraws its stylet, leaving a puncture wound that may appear as a tiny red papule. The host’s immune response to flea saliva often produces a localized itch, erythema, and, in some individuals, a small wheal or vesicle.
Key points of the biting mechanism:
- Jump onto host → firm grip using hind legs.
- Penetrate skin with stylet at 30–45° angle.
- Inject saliva containing anticoagulants and anesthetics.
- Suck blood via maxillary canal; contract foregut to ingest.
- Withdraw stylet, leaving a puncture that elicits an inflammatory reaction.
Repeated bites can lead to secondary bacterial infection if the skin is scratched, and hypersensitivity in some people may cause larger wheals or a rash resembling papular urticaria. Understanding the anatomical and biochemical aspects of flea feeding clarifies why bites are often painless at first yet become intensely itchy shortly after.