Trypophobia is described as the fear of a cluster of irregular-shaped circles or holes, such as the holes in a sponge, honeycomb, or bubbles in a coffee cup. These shapes might seem innocent enough to most people, but just looking at images of these holes can be enough to provoke intense feelings of fear, anxiety, and aversion in some people.

Psychologists from the University of Kent in the UK believe they have found the cause of this condition: a deep-seated aversion to parasites and disease.

Their study, recently published in the journal Cognition and Emotion, suggests that the condition is related to an evolutionary response to avoid infectious diseases or parasitic infection. As they highlight, many nasty infections entail circular patterns and holes, such as tics, botflies, smallpox, measles, rubella, typhus, scarlet fever, etc.

It’s a well-established fact that many responses of disgust and aversion stem from an evolutionary function to avoid sources of infection. For example, many people are disgusted by blood and bad smells, which serves to deter them from possible sources of sickness.

For their study, the team recruited over 600 people, half with trypophobia and half without, to view 16 images of holes and clusters, along with answering a questionnaire. Eight of the images were pictures related to diseased body parts, like rashes or embedded ticks, while the other eight had no relevance to diseases, such as drilled holes in a wall and a seed pod.

The eight disease-related images provoked a negative response among both groups. However, the non-disease-related images only provoked this response in the people with trypophobia.

Individuals with trypophobia also reported feelings of disgust, nausea, or the urge to vomit when they viewed these images. They also said they experienced sensations like skin itching, skin crawling, or the sensation of bugs crawling on the skin. Once more, this reaffirmed the theory that people with trypophobia may perceive cluster stimuli as if they are harbingers of parasites and disease.

Like many of our fears, it’s simply a deep-rooted response – in this case, possibly an overgeneralized anxiety about parasites and infectious diseases.