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Acarophobia (Imagined Infestation)
Acarophobia (from the Greek akari, meaning mite, and phobos, meaning fear), also
known as delusional parasitosis, delusional infestation, or Ekbom’s syndrome, is
a psychiatric disorder in which individuals erroneously believe that their skin and
body are infested with parasites. The term acarophobia was coined by Thibierge,
a French dermatologist, in 1894, and it is now considered to be a misnomer since
the disorder is not characterized by phobic fear but rather by delusional beliefs. The
term entomophobia (fear of insects) has also been inaccurately used to describe
the disorder and similarly pertains to fear rather than false beliefs. Contemporary
clinicians and researchers prefer to use the terms delusional parasitosis or delu-
sional infestation. In cases where fear or anxiety is present, it is thought to be a
consequence of the delusions.
Delusional parasitosis is not uniform in its presentation and can occur either in
primary form, as a stand-alone psychiatric disorder, or in secondary form, as a con-
sequence of a medical condition, mental disorder, or intoxication. In its primary
form, delusional parasitosis is classified in the Diagnostic and Statistical Manual
of Mental Disorders, fifth edition as a type of psychotic disorder called delusional
disorder, somatic type. Causes of the secondary form of delusional parasitosis vary
widely and can include cerebrovascular disease, cancer, dementia, schizophrenia,
major depression, and chronic use of substances (e.g., methamphetamine, cocaine,
alcohol), among others. The prevalence of delusional parasitosis is not known, but
researchers believe that it is more common than was once thought. The primary
form of delusional parasitosis is more common in women than in men, with the
average age of onset ranging from 50 to 69 years. The cause of the disorder is not
well understood. Hypotheses about its origins have focused on the possible misper-
ception of actual physical sensations that subsequently become associated with par-
anoid ideas, and on the role of neurotransmitters such as dopamine and serotonin.
The hallmark feature of delusional parasitosis is the fixed belief that one is
infested by parasites or very small “bugs” or insects. In some cases, individu-
als with delusional parasitosis also believe that their family members, friends,
pets, home, and belongings are infested. They commonly report that they feel
itching and other physical sensations, such as crawling and biting, on their skin
and bodies. Their beliefs about being infested persist despite a lack of evidence
upon medical examination and microbiological analysis. Behaviors commonly
