What are external parasites known for doing?

External parasites are primarily known for feeding on other living organisms, which is what makes them distinct. These organisms rely on a host for nourishment, deriving their sustenance directly from the host's body, either through direct contact with the host's skin or by drawing nutrients from its blood. This feeding process can lead to various health issues for the host, including irritation, allergic reactions, and in some cases, transmission of diseases.

Living independently of their host would contradict the very nature of what a parasite is, as parasites depend on their hosts to survive. Additionally, while some organisms can spread through the air, external parasites typically require direct contact or remnants of the host's biological material to spread, which primarily occurs through physical interaction. Lastly, reproducing exponentially in water is more characteristic of certain organisms like bacteria or certain aquatic species, rather than external parasites, which prefer to be on or within a host.

Understanding these mechanisms helps in the comprehension of how external parasites affect both human and animal health.