A child being sprayed with Aerogard

A child being sprayed with Aerogard

Credit: CSIRO

Aerogard protects us from mosquitoes and other pesky bugs whilst outdoors. But did you know that it was originally made to keep blowflies away from sheep’s butts?

Blowflies are a pest in Australia and have been a real problem for sheep. The flies lay eggs in the sheep’s wool and can introduce diseases through cuts on the sheep.

In 1938, Dr Douglas Waterhouse, the creator of Aerogard, began researching how to protect sheep. He discovered a chemical mixture that could be applied to a bandage to kill the blowflies laid on a sheep.

Soon after his invention, WWII broke out.

After joining the war effort, Dr. Waterhouse’s boss returned to Australia to research how to keep soldiers safe from mosquitoes. Dr. Waterhouse began researching oils to spray on the water where mosquitos hatch, killing them before they could spread diseases.

An Australian Sheep Blowfly, Lucilia cuprina.

Credit: CSIRO

When this technique didn’t quite work, Dr. Waterhouse turned to protecting the soldiers themselves. With a tip-off from the Standard Oil Company, he found that the chemical dimethyl phthalate worked wonders as a safe repellent.

Soldiers nicknamed the solution ‘Mary’, and it was widely used until the end of the war. In 1963, it was brought into fashion with the wider public by Queen Elizabeth II, who wore the repellent to a game of golf. Days later, representatives for the company Mortein called Dr. Waterhouse and asked him for the formula – which he gave to them for free!

How does Aerogard work?

The main chemical now used in Aerogard (diethyltoluamide, also known as DEET) is different to Dr. Waterhouse’s dimethyl phthalate. But the two chemicals repel mosquitoes for the same reason: mosquitoes just don’t like the taste or smell! When a mosquito lands on a person covered in insect repellent, they taste the repellent through their feet, and they hate the taste, so they leave!

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