Flashback Friday: Chest waxers beware: body hair protects against bedbugs.

By Seriously Science | December 12, 2014 6:00 am
Photo: flickr/vince42

Photo: flickr/vince42

Scientists have long speculated about why humans have so little body hair compared with other primates. (The most widely accepted explanation is that less body hair allowed for more efficient cooling on the savannahs where humans evolved.) However, less attention has been paid to the fine coating of hair that we have retained. In this study, the researchers set out to test their hypothesis that our fine body hair serves to defend us against “ectoparasites”–that is, bloodsucking insects like bedbugs. To do so, they shaved one arm of each subject and then released a bedbug onto each arm (one shaved, one unshaved). The researchers then asked the subjects to count how often they “perceived the presence of something on their arm” (see full methods description below). Turns out that shaving the arms not only made it easier for the bedbugs to bite, but also made them harder to detect. This makes intuitive sense–the tiny hairs on your arm obstruct the bug’s passage and make it more likely that you’ll feel it moving around. The authors conclude that body hair might have been kept for precisely this reason. Something to consider the next time you head to the waxing salon…

Human fine body hair enhances ectoparasite detection

“Although we are relatively naked in comparison with other primates, the human body is covered in a layer of fine hair (vellus and terminal hair) at a relatively high follicular density. There are relatively few explanations for the evolutionary maintenance of this type of human hair. Here, we experimentally test the hypothesis that human fine body hair plays a defensive function against ectoparasites (bed bugs).

Our results show that fine body hair enhances the detection of ectoparasites through the combined effects of (i) increasing the parasite’s search time and (ii) enhancing its detection.”

Bonus excerpt from the full text:

“(c) Experimental treatment
The experimental procedure required that each host was tested on a shaved and unshaved arm (randomized with respect to arm and temporal sequence). The treatment arm was shaved on the upper surface between the wrist and the elbow with a new razor (Gillette Mach 4), while using the same brand of perfume- and colour-free soap (Simple). A rectangle measuring 5 × 10 cm was then drawn on the shaved area with a marker pen and vaseline (a barrier to bed bug locomotion) applied to the marked boundary. This ensured each host experienced the same potential surface contact with the parasites. Testing on the unshaved (control) arm was preceded by washing the unshaven arm with the same soap as the treatment, and generating a vaseline-delimited rectangle as in the treatment.

Each host was given a tally-counter and asked to look away as a bed bug was placed within the vaseline rectangle on their arm. Prior to release, all bed bugs experienced the same handling conditions. The volunteer was instructed to use the tally-counter every time they perceived the presence of something on their arm. The experimenter timed the duration of search behaviour of the bed bug on the host’s arm and removed the insect as it extended its proboscis (the stereotyped pre-feeding behaviour). The search time was recorded as the time between placement on the host and extension of the proboscis. Host tally-counts were used as an index of parasite ‘detections’.”

Related content:
Flashback Friday: Innocent until proven bearded.
NCBI ROFL: Frequency of pubic hair transfer during sexual intercourse.
NCBI ROFL: What is this I don’t even (facial hair edition).

  • Dahai Dong

    Right method immediately stops bed bug bites forever after
    one-time easy job no matter how many bed bugs are behind wall and under carpet,
    or migrate from other apartments. Google “bed sized bed bug trap” to convert
    entire bed into a trap with sleeper as inaccessible CO2 bait. Bed bugs can’t
    fall from ceiling to bed after Scotch slippery barrier is applied on ceiling.
    Don’t waste time on vacuum, steam, chemical, DE, encasements, dumping
    furniture, and searching bed bugs. Searching bed bugs instead of letting every
    bed bug suicide is as nonsense as preferring endless cycles of killing,
    feeding, and laying eggs instead of celebrating having solved problem today due
    to no more bites and negligible daily effort. It is nonsense to expect bed
    bug’s one year life. Catch bed bugs into 2 glass jars. Send one jar into a
    refrigerator for one year and leave the other jar without cap in bedroom for
    bed bugs to feel CO2, crawl every night without dormant, and starve in weeks.
    More than 99% bed bug feeding is at night. Sleeping in bathtub eliminates the
    feeding. Bed sized trap functions better than bathtub. Exterminators don’t feel
    difficult to keep their bodies bed bugs free at day time. Neither do you.
    Common sense is good enough to confirm how easy to keep your body bed bugs free
    24 hours a day no matter how many bed bugs are at home. Use of mattress
    encasement instead of bed sized trap is as nonsense as sleeping outside tent
    which is used as bush encasement to seal mosquitoes inside bush. Spending
    thousands of dollars on heating house instead of cheap bed sized trap is as
    nonsense as heating house instead of poison bait to kill ants. Americans should
    not have spent $40 million and $200 million annually on mattress encasements
    and heating houses, respectively, if people knew the innovative product.
    Investors are wanted.


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