Body Hair– A Barrier Against Bed Bug Bites

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People have finer body hair, compared with other species. It has always played an important role in thermoregulation by keeping heat. However, does it also serve other purpose? The answer is yes. Because of this fine body hair, we are able to sense a parasitic insect’s presence in our skin; more importantly, it keeps them from biting us. These were revealed from the recent study made by researchers at the University of Sheffield, UK, published online last December 14 in the Biology Letters, a Royal Society journal.

Despite the common observation that humans are less ‘covered’ than other primates, two kinds of fine hair are actually present in our skin. Vellus is the first kind; it is short and less likely to be noticed.  The longer and more noticeable terminal hair is the other kind. Also, skin follicles have closer distance. While the human body hair’s evolutionary maintenance still remains not that clear according to the researchers, looking into its role against bed bugs is something they aim. The persons in-charge of the study include first author and Sheffield Zoology graduate Isabelle Dean, who chose this as focus of her honors project, and Professor Michael Siva-Jothy from the University’s Department of Animal and Plant Sciences, who supervised the former.

The researchers included 29 healthy volunteers, with one arm shaved and another with hairs present. Afterwards, hungry ectoparasites were placed on the skin of both arms. They discovered the two mechanisms by which our body hair benefits us. First, it augment the bug’s time in locating the appropriate are to begin blood-sucking; second, it is easier for us to sense their presence on our skin.  Furthermore, the participants who had greater hair layers slowed the insects’ time in looking for a perfect sucking spot in their arms. The researcher also assisted in seeking why body parts (i.e. wrists and ankles) with less hair being more prone to parasite bites, with the likes of mosquitoes, leeches, midges and ticks.

According to Siva-Jothy, we are able to detect displacement because of the presence of nerves in our hairs. These hairs create a barrier against parasites. Moreover, search time for these insects becomes delayed and we are more likely able to detect their presence, since they have to take time in searching in our skin.

The researchers believe that their study results may give light in knowing the reason behind the evolutionary transformation in our body hair, from our ancestors’ thick covering (which is still evident in other primates) to the current fine hair we have.  Siva-Jothy elaborated that if we still have thick hairs it would be hard for us to exactly locate them, although we can detect them, because parasites can easily hide. Siva-Jothy cited, “Our proposal is that we can retain the fine covering because it aids detection and if we lost all hair, even the relatively invisible fine hair, our detection ability goes right down.”

Siva-Jothy, with his colleagues, is currently studying blood-sucking insects’ biology, their reproduction and immunity. Also, they are seeking novel means of parasite control, so that we can improve the measures of minimizing transmission of diseases acquired from insects. Furthermore, he stated that, by nature, blood-sucking insects will tend to select areas with less hair as sucking sites.

 

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