Monday, 19 December 2011

Body Hair as Parasite Protection

Does your body hair help you notice when something is crawling around looking for a place to bite? Does it discourage that ectoparasite from biting? Authors Isabelle Dean and Michael T. Siva-Jothy think the answer to both questions is ‘yes.’ A report in Biology Letters reveals the findings of a study that was designed to reveal whether our fine body hairs protect us from ectoparasites such as bedbugs.

Body hair appears to slow bedbugs down; the hairier
you are, the better! Image by Jiří Humpolíček
CC BY-SA 2.5

Bedbugs Are Slower on Hairy Skin

In a study of twenty-nine student volunteers, the researchers noted that bedbugs took longer to select a feeding site on hairy, as opposed to shaven, skin, (and the hairier the better) and that the volunteers were better able to detect the insects on unshaven skin. Thus, having all those fine hairs apparently helps us, in two different ways, to notice the bug before it bites.

Dean and Siva-Jothy point out that it’s already been shown that some insects that bite animals, including bedbug relatives, prefer to bite on relatively hairless parts of the body. It’s easy to see that such behavior would tend to favor bug survival if the bug goes unnoticed. In some circumstances, we can also see that hairier humans might have a survival advantage.

Does Body Hair Slow All Ectoparasites Down?

This study only looked at bedbugs; it would be interesting to see if the same thing happens with ticks (I can attest from personal experience that ticks have an amazing ability to traverse large areas of skin without ever being felt), kissing bugs, mosquitoes, black flies and other biting insects and arachnids.

So we know one possible reason why we have all those fine hairs all over us – and why we perhaps shouldn’t be shaving them off in a time of bedbug resurgence and increased tick-transmitted disease.

Dean, Isabelle, and Michael T. Siva-Jothy. “Human fine body hair enhances ectoparasite detection.” Biology Letters: Published online December 14, 2011, doi: 10.1098/rsbl.2011.0987

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