Parasites are opportunistic organisms that have learned to benefit from the toil of others by sapping them of their resources, sometimes in ways so covert the host doesn’t even realize they’re harboring a freeloader (you could have face mites on you right now). Other parasites are not so good at keeping their presence unknown (like the mushroom that burst out an ant's butt), triggering symptoms that can vary from the benign to life-threatening depending on their severity (if you're curious as to what it's like, you can hear the firsthand account of a scientist who volunteered to have 50 hookworms wriggle into his system).
Lice are an example of a parasite that enjoys hanging out on humans, and many of us will likely have firsthand experience after rubbing heads a little too enthusiastically during our school years. There are many different types of lice and each has its own niche. For Phthirus pubis, commonly known as pubic lice or crabs, that niche is genitals.
Crabs are tiny and so named for the fact they look a bit like the beach-going crustaceans having big claws, but here the similarities end. Dependent on blood, these lice can’t survive for long periods of time without a host but can pass from person to person. Sexual or physical contact between an infected and uninfected person is the most effective method for transportation, and while some have suggested crabs may also travel on surfaces such as towels, this is not unanimously supported. Unfortunately, crabs’ preferred habitats aren’t limited to the pubic area and if you should run face-first into lice town, they can even take up residence in your eyelashes.
According to a paper on NCBI, when a person’s eyelashes become parasitized by crabs in this way, it’s referred to as Phthiriasis palpebrarum (also known as phthiriasis ciliaris, or ciliary phthiriasis). The adult crabs are just 2 millimeters (0.07 inches) long making them smaller than lice commonly found in the hair. They have claws used for clinging onto hair, which is why they’re partial to the pubic area, but they can spread to other fuzzy parts of the body if their host provides suitable playgrounds.
They have quite the appetite, both in a digestive and reproductive sense, feeding around five times a day while females churn out an average of 3 eggs daily. These then hatch into crabs roughly a week later, so it’s easy to see how a single trespasser can quickly become an established colony.
Fortunately, there are several methods for removing an eyelash crab infection, one of which includes dousing the lice with Botox so that they become paralyzed and willingly slip off the lashes. However, as the best method varies depending on the patient’s particular circumstances, it’s always best to check with your regular doctor before trying any DIY removals.