The concern about insects or arachnids crawling on a person while they sleep is a common worry, fueled by folklore and a natural aversion to the unseen. While the idea of being a host to a constant parade of nighttime visitors is generally inaccurate, some nocturnal encounters do occur. The reality involves a distinction between organisms that actively seek a sleeping human for sustenance and those that are merely accidental wanderers. Understanding the specific behaviors of these “crawlers” helps separate unfounded fears from actual risks.
The Reality of Nocturnal Encounters
Nocturnal activity is defined by two distinct types: parasitic feeding and incidental movement. Most interactions are microscopic or highly incidental, meaning the vast majority of insects and arachnids are not purposefully seeking out a sleeping person. Organisms that feed on blood or skin are attracted by biological signals, while others are simply navigating the environment and may accidentally cross a person’s path. These interactions are rarely malicious, but the outcomes can range from a simple nuisance to a localized skin reaction.
Bugs That Actively Seek a Host
A small group of arthropods actively seeks out a sleeping person because they are obligate parasites, requiring a blood meal to survive and reproduce. Bed bugs, for example, are small, reddish-brown insects that emerge from hiding spots like mattress seams and crevices primarily before dawn. They locate hosts by detecting exhaled carbon dioxide and body warmth. Once a feeding site is found, the bed bug draws blood for approximately three to twelve minutes before crawling away to digest its meal.
Another microscopic arthropod that targets a sleeping host is the Sarcoptes scabiei mite, which causes scabies. These mites burrow into the upper layer of human skin, where the female deposits eggs, leading to an intense allergic reaction and severe itching that often worsens at night. Fleas, though often preferring pets, can also feed on humans while they sleep, especially if an infestation is severe or if the primary host is absent.
Accidental Visitors and Harmless Crawlers
Most arthropods that might accidentally enter a sleeping area are not seeking a human host for food or shelter. Spiders, a common fear, are largely averse to human contact and are not attracted to the carbon dioxide or warmth produced by a sleeper. The massive size and movement of a sleeping human are typically deterrents, leading them to quickly retreat if they accidentally wander onto the bed. The widespread myth about a person swallowing spiders in their sleep is biologically unfounded.
Other household arthropods, like ants, cockroaches, or house centipedes, are also accidental visitors, usually drawn by moisture, food scraps, or other pest prey. Cockroaches have been known to occasionally nibble on skin flakes or eyelashes but do not rely on humans as a food source. House centipedes are predators of other insects and actively avoid humans, only appearing if their hiding places are disturbed. These non-parasitic encounters are rare and are a byproduct of these creatures navigating the home environment.
Strategies for Minimizing Unwanted Company
Preventing nocturnal encounters involves implementing environmental controls that make the bedroom less hospitable to all types of crawlers. One effective method is reducing the clutter around the bed, which eliminates the hiding spots for parasitic insects like bed bugs. Using protective, zippered mattress and box spring encasements creates a barrier that traps any existing bed bugs and prevents new ones from establishing themselves. Laundering bedding, curtains, and clothing frequently in hot water can also help eliminate hitchhiking insects or mites.
For general household pests and accidental visitors, sealing cracks and crevices in the walls, floors, and around utility lines is important, as these are common entry points. Regular and thorough vacuuming, especially around the bed and baseboards, removes both potential pests and the food sources that attract them.