Why do horses roll in dirt?

We recently read the story of David Whitlock, an inventor, who risked everything by spending all his money on patent filings for a type of bacteria, related to the skin microbiome.

Whitlock’s creativity about bacteria was catalysed when a teacher asked him why did her horse roll in the dirt, regardless of the weather conditions?

Typically the answer to this question links to UV protection or repelling insects. However, Whitlock knew this was not the case – this one question kickstarted a fateful set of events.  Upon doing more research, he became intrigued by a type of bacteria which is found in soil and derives from ammonia and not organic matter.

It was through the fascination of this environment that Whitlock pondered if these ammonia-oxidizing bacteria turned sweat into a beneficial substance? Further research proved his hypothesis to be true: ammonia-oxidizing bacteria converts ammonia into nitrite (a molecule with anti-infective properties) and nitric oxide.

In fact, nitric oxide helps to maintain blood pressure by dilating blood vessels – this helps kill foreign invaders in the immune system. It was also found that nitric oxide can be a biochemical mediator of penile erections and possibly a biochemical component of long-term memory. [1]

So, we now know the horses experienced a range of health benefits by rolling in dirt – and may have inspired a new wave of skin care products in the process.


[1] https://science.sciencemag.org/content/258/5090/1861

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