The understanding of<unk>  is limited. Several possible causes have been proposed. Geoff Cole and Arnold Wilkins believe the reaction is an "unconscious reflex reaction" based on a biological revulsion, rather than a learned cultural fear. Imagery of various venomous animals (for example, certain types of snakes, insects, and spiders) have visual characteristics similar to<unk>  imagery. Because of this, it is hypothesized that<unk>  has an evolutionary basis meant to alert humans of dangerous organisms. Can et al., however, believe the connection between<unk>  and evolution as a result of a threat from deadly creatures to be weak and that, if a connection does exist, it manifests later in life rather than in childhood. Martínez-Aguayo et al. described<unk>  as usually involving "an intense and disproportionate fear towards holes, repetitive patterns, protrusions, etc., and, in general, images that present high-contrast energy at low and midrange spatial frequencies." Cole and Wilkins also stated the imagery has high spatial frequency with greater energy at midrange. Whether together or separate, it appears that low and midrange spatial frequencies are necessary for inducing<unk>  reactions. Based on the imagery's visual cues, An Trong Dinh Le, Cole, and Wilkins developed a symptom questionnaire that they believe can be used to identify<unk> . Researchers have also speculated that<unk>  reactions could be perceived as cues to infectious disease, which could be alerts that give one a survival advantage. In a study by Kupfer and Le,<unk>  and non-trypophobic participants showed significant aversion to disease-relevant cluster images, but only<unk>  participants displayed a significant aversion to disease-irrelevant cluster images. Martínez-Aguayo et al. stated that, because the reactions could not be attributed to different sensitivity levels or neuroticism differences, Kupfer and Le believe it supports their hypothesis that<unk>  is "an overgeneralized aversion towards cluster stimuli that indicates a parasitic and infectious disease threat". Yamada and Sasaki also propose that<unk>  reactions are due to the imagery's visual similarities to skin diseases. Whether<unk>  is associated with obsessive–compulsive disorder (OCD) has also been studied. A significant minority of those with<unk>  meet the DSM-5 criteria for an obsessive-compulsive disorder. Martínez-Aguayo et al. stated that other findings refer to<unk>  having common comorbid psychiatric diagnosis, such as major depressive disorder or generalized anxiety disorder, although Le et al. felt that general anxiety does not cause<unk> .
Trypophobia
Phonophobia
Thermophobia
Pseudophobia
Neophobia
Phagophobia
Hodophobia
Thalassophobia