If you think about it, trypophobia — or fear of holes — isn't that strange. Holes can get you into trouble; think about falling into a well or being sucked into sinkholes. Conversely, strange things often crawling out of holes, and all these scenarios could potentially cause injury or death.

"Trypophobia" was coined online in 2005 by those who experience the fear. You can check out the Facebook group to read about sufferers' experiences. Most people who say they have trypophobia are disgusted by items, typically organic in nature, that have holes in them. Think Swiss cheese, coral, sponges, Ethiopian Injera bread and lotus seedheads, for example. But they might not be true phobics. A phobia is more of an extreme fear or terror. The American Psychiatric Association's "Diagnostic and Statistical Manual of Mental Disorders" says to be a real phobia, it must interfere "significantly with the person's normal routine."

swiss-cheese Swiss cheese may not always have holes in it, due to changes in milk processing, but as long as it does, some people will find it objectionable. (Photo: Africa Studio/Shutterstock)

Psychiatrist Carol Mathews told NPR, "There might really be people out there with phobias to holes, because people can really have a phobia to anything, but just reading what's on the Internet, that doesn't seem to be what people actually have." Whether you're genuinely phobic to things with holes in them or just feel generally uncomfortable looking at them, researchers have been looking into the phenomenon in recent years.

lotus seed Some people are uncomfortable by the holes in lotus seed heads. (Photo: battler/Shutterstock)

Was this discomfort with hole-y images an unconscious reaction, as people said it was? And if so, what could be causing it? In 2013, the aptly titled paper "Fear of Holes" was published. Scientists at the Center for Brain Science at the University of Essex in England sourced a number of images that trypophobics had identified as causing a negative reaction and did a spectral analysis on them. They found that the images had a spectral pattern "associated with uncomfortable visual images, namely, high-contrast energy at midrange spatial frequencies." So there was a similarity between the types and spacing of holes in the images trypophobics found alarming and other uncomfortable visual images.

"Critically, we found that a range of potentially dangerous animals also possess this spectral characteristic. We argue that although sufferers are not conscious of the association, the phobia arises in part because the inducing stimuli share basic visual characteristics with dangerous organisms, characteristics that are low level and easily computed, and therefore facilitate a rapid nonconscious response," the researchers wrote in the abstract for the paper.

ancient sponge A fossil sponge from the Cretaceous. It would have lived hundreds of millions of years after its first sponge ancestors. (Photo: Wiki Commons)

And in a 2015 paper, another set of researchers developed a trypophobia test. "The trypophobia questionnaire (TQ) was based on reports of various symptom types, but it nevertheless demonstrated a single construct, with high internal consistency and test-retest reliability," the scientists wrote in their abstract. With such a test available, it becomes closer to possible that this sensitivity isn't just "all made up," as some critics have asserted.

But what are these innocent corals, sponges, cakes and bubbled chocolates reminding people of deep-down that's causing such a reaction? There seem to be two main theories. From the Essex study, the spectral pattern is associated with other "uncomfortable images" — those images were of skin colorations of dangerous or poisonous animals. Even people without trypophobia find some of those patterns disquieting to look at.

A boulder coral undergoing a bleaching event in Raja Ampat, Indonesia.A boulder coral undergoing a bleaching event in Raja Ampat, Indonesia. (Photo: Ethan Daniels/Shutterstock)

Another theory is that throughout human history, sores, boils, scars, and other skin lesions were much more common than today, and we have a built in disgust of them because some of those skin issues can be contagious. Staying away from them, or the people who had them, might have kept our ancient ancestors healthier than those who didn't avoid these skin problems. We get a bit of this perspective from a trypophobic on Facebook, who wrote: "I was stung by a bee in high school on my outer thigh. I had an allergic reaction, and my skin started to swell. The swelling was so bad,I could see each individual pore on my leg and I freaked out. Since then, I have not been able to look at clusters of holes without getting the heebie-jeebies."

And what about the opposite? I find many of the above images attractive and interesting (but I also have a penchant for bugs and spiders, snakes and reptiles). Could there be such a thing as trypophilia?

So even though this phobia may have gotten initial recognition as people on the internet bonded over their shared revulsion, there may be something more to it, though researchers haven't solved the mystery yet.

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.