Origin
Bars of Irish Spring soap are marketed as a product to, you know, keep yourself clean. But according to the internet, these bars of soap have several other uses. Some websites claim that the soap keeps away mice, while others say it keeps away deer. One of the most popular assertions, however, is that Irish Spring Soap can be used to repel flies.
One viral Facebook post shared by Tabe Paxon in July 2020 read:
Has anyone else noticed how bad flies are this year? Well I googled how to keep them away and..... who knew Irish spring original scent would really work???? I’m amazed lol. Easily amazed I guess. Dad and me sit on the back porch a lot and dad even had a fly swatted out here with him bc they where so bad. Hung one bar of Irish spring and shocked how quickly and well it works. Thought I would share for anyone else annoyed with the flies
The claim that Irish Spring soap repels flies has been amplified by a variety of home and gardening websites, such as grandmasthing.com, Homemaking.com, and even Buzzfeed.
We're skeptical of this fly repellent solution for a few reasons. For starters, the sources we found pushing this claim don't provide much information as to why this works. Instead, the blogs offer vague and unsupported claims about how flies apparently don't like the smell. But that just doesn't pass the sniff test.
Second, if Colgate-Palmolive, the company that owns the Irish Spring brand, truly had their hands on an effective insect repellent, why wouldn't they market it as such? Why wouldn't they make a product specifically targeting this need?
Lastly, we have not found any credible studies or experiments documenting whether hanging a bar of Irish Spring Soap effectively repelled flies. In fact, the only unofficial experiment found appeared to show the exact opposite. In June 2021, the Pine Meadows Hobby Farm, a frugal homestead in the Cascade Mountains that creates video tutorials for their YouTube page, posted a little experiment to see if Irish Spring Soap truly repelled flies. The results? The soap did not seem to have any impact on the pest problem:
https://www.youtube.com/watch?v=0bGa9jvK11s
We reached out to Colgate-Palmolive and the American Horticulture Society, and we will update this article if more information is made available.