British scientists have proved a hypothesis that said human fine body hair plays a defensive function against parasites such as bed bugs and fleas.
The results of the study by Isabelle Dean and Michael Siva-Jothy from University of Sheffield, published in the journal Biology Letters, show that fine body hair enhances the detection of parasites through two effects: increasing the parasite’s search time and enhancing its detection.
A bed bug Cimex lectularius (Piotr Naskrecki / Gary Alpert / Harold Harlan / Richard Pollack / CDC/ Harvard University)
For their study, the researchers recruited twenty-nine student volunteers in the University of Sheffield through opportunity sampling on the social networking site Facebook.
The experimental procedure required that each volunteer had to be tested on a shaved and unshaved arm: once on one arm, and then a week later on the other.
The researchers placed hungry human bed bugs (Cimex lectularius) on skin of volunteers and measured the duration of search behavior of these insects. They found that the parasites had to search for longer to find somewhere to feed on hosts with much hairier arms.
“Our data suggest that reduced body hair in humans functions, at least partly, as a defense against ectoparasites,” said researchers.
“On the basis of our results, and our conclusion that fine body hair functions to enhance ectoparasite detection, we predict that transient ectoparasites should show feeding preferences for relatively hairless parts of their host’s body.”
