A documentary revealed that one out of every seven Scots can naturally repel midges.

Midges are prevalent in Scotland and can cause painful bites and even disease but, as featured in the BBC Scotland based documentary The Secret Life of Midges, scientist were able to find that one in seven Scots that have high levels of ketone are natural midge repellents.

"As many as one in seven of us may be natural midge repellers," said entomologist Dr. James Logan of the London School of Hygiene and Tropical Medicine, who is leading a study on how some people appear to be naturally protected from midge bites.

Last summer, he and his team enlisted 23 volunteers and exposed them to midges under different conditions to find who among them are natural midge repellents. The volunteers were divided into groups, and for every group, there was at least one who didn't attract as much midges as the others.

Logan's past research indicated that the fruity smelling compound, ketones, which can be found in human sweat, was a possible cause for this reaction.

"By isolating the chemicals as part of our body odor, we have been able to identify (why some people) don't get bitten," said Logan. "They...produce these extra chemicals that are repellent to midges."

Logan was also able to determine that the ability to make enough ketones for the body to have a natural repellent is genetic and can be passed on. The next step was to identify which genes directly affect what makes some people unattractive to midges.

The researchers hope that, by finding this gene, a treatment could be developed to make other people unattractive to midges as well.

Midges, or sand flies, are mostly harmless, but one variety, the Culicoides impunctatus, has a taste for blood and would often bite humans and other animals in groups, leaving irritating bites and can even cause the disease called Leishmaniasis.

According to the Centers for Disease Prevention and Control, Leishmaniasis is caused by a parasite that can be transmitted by an infected midge bite. There are two forms of the disorder: the cutaneous, or skin, leishmaniasis that causes sores and ulcers on the skin, and visceral leishmaniasis that affects internal organs like the spleen and liver that can be life threatening.

Midges have been around since ancient times and can be found in different parts of the world, though Scotland has one of the highest population of biting midges in the world.

"We have estimated that 40,000 could land on your arm in one hour," Logan said. "They haven't changed for millions of years for a reason - they are the ultimate blood seeking machines."

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