Since the advent of the internet, people have been able to discuss their symptoms with others globally. Sometimes people with very unusual symptoms discover others with similar experiences, which they are then able to discuss without fear of ridicule. Discussion forums and support groups are formed and eventually a new medical condition may be recognised. A case in point is "visual snow", which individuals experience as bright dots persistently floating like snow across their vision. Another is trypophobia.
Trypophobia – a "fear of holes" – is a condition which triggers individuals to suffer an emotional reaction when viewing seemingly innocuous images of clusters of objects, usually holes. The condition was first described on the internet in 2005 though it is not yet a recognised medical diagnosis.
The images responsible for the emotion include natural objects such as honeycomb or the lotus seed head, and man-made objects such as aerated chocolate or stacked industrial pipes viewed end-on. Despite their seemingly innocuous nature, images such as these (ideal for sharing on the internet) can induce a variety of symptoms including cognitive changes that reflect anxiety, bodily symptoms that are skin-related (such as itchiness and goose-bumps), and physiological changes (such as nausea, a racing heart, or trouble catching breath).
The images that induce the emotional reaction would not normally be conceived of as threatening so, in this respect, trypophobia differs from many other phobias.
Phobias are anxiety disorders that are normally thought to arise because of learning (a dog bite may lead to a fear of dogs) or because of innate evolutionary mechanisms such as may underlie a fear of spiders and snakes. Usually, there is a threat, specific or general, real or imagined.
In the case of trypophobia, there is no obvious threat, and the range of images that induce the phobia have very little in common with one another, other than their configuration.
It appears that it is this configuration that holds the key to the emotion that the images induce. Individuals who do not profess trypophobia still find trypophobic images aversive, although they do not experience the emotion. They do so because the configuration gives the image mathematical properties that are shared by most images that cause visual discomfort, eyestrain or headache.
Images with these mathematical properties cannot be processed efficiently by the brain and therefore require more brain oxygenation. In a paper, Paul Hibbard and I proposed that the discomfort occurs precisely because people avoid looking at the images because they require excessive brain oxygenation. (The brain uses about 20% of the body's energy, and its energy usage needs to be kept to a minimum.)
So trypophobic images are among those that are intrinsically uncomfortable to look at, and we are now investigating why it is that some people and not others experience an emotional response.
Images of contaminants such as mould and skin diseases can provoke disgust in most people, not just those with trypophobia. The disgust is probably an evolutionary mechanism that promotes avoidance and has survival value.
Images of mould and skin lesions have mathematical properties similar to those of images that are trypophobic and our current work explores whether they also induce a large oxygenation of the brain in addition to being generally uncomfortable. Perhaps discomfort is a useful mechanism not only for avoiding excessive oxygenation, but also for rapidly avoiding objects that provide a threat in terms of contamination. It may be that in people with trypophobia, the mechanism is overworking.