A less well-known and uncommon but important paresthesia is formication, the sensation of insects crawling underneath the skin.
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Causes of formication include normal states such as onset of menopause (i.e. hormone withdrawal). Other causes are medical conditions such as pesticide exposure, mercury poisoning, diabetic neuropathy, skin cancer, syphilis, Lyme disease, hypocalcaemia or herpes zoster (shingles) and neurocysticercosis. Formication can be a result of stimulant intoxication or withdrawal (methamphetamine, cocaine, MDMA aka ecstasy) or alcohol withdrawal in alcoholics (i.e.
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Tactile hallucinations are the illusion of tactile sensory input, simulating various types of pressure to the skin or other organs. One subtype of tactile hallucination, formication, is the sensation of insects crawling underneath the skin and is frequently associated with prolonged cocaine use. However, formication may also be the result of normal hormonal changes such as menopause, or disorders such as peripheral neuropathy, high fevers, Lyme disease, skin cancer, and more.
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Formication is the sensation that resembles that of small insects crawling on (or under) the skin when there is nothing there. It is one specific form of a set of sensations known as paresthesias, which also include the more common prickling, tingling sensation known as "pins and needles". Formication is a well documented symptom, which has numerous possible causes. The word is derived from formica, the Latin word for ant.
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Formication may sometimes be experienced as feelings of itchiness, tingling, pins and needles, burning, or even pain. When formication is perceived as itchiness, it may trigger the scratch reflex, and because of this, some people who experience the sensation are at risk of causing skin damage through excessive scratching. In some instances, static electricity can attract particulates to the skin and can also cause body hair to move, giving a sensation like insects crawling over the skin. However, in many cases no external trigger creates the sensation.
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Formication is etymologically derived from the Latin word formica, meaning "ant", precisely because of this similarity in sensation to that of crawling insects. The term has been in use for several hundred years. In the 1797 edition of the Encyclopædia Britannica, a description of the condition raphania includes the symptom: Described again in an instructional text from 1890: > A variety of itching, often encountered in the eczema of elderly people, is > formication; this is described as exactly like the crawling of myriads of > animals over the skin. It is probably due to the successive irritation of > nerve fibrils in the skin.
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Common side effects of ioflupane (123I) are headache, vertigo, increased appetite and formication. Less than 1% of patients experience pain at the injection site. The radiation risks are reported as low. The committed effective dose for a single investigation on a 70 kg individual is 4.6 mSv.
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Cocaine has a similar potential to induce temporary psychosis with more than half of cocaine abusers reporting at least some psychotic symptoms at some point. Typical symptoms of sufferers include paranoid delusions that they are being followed and that their drug use is being watched, accompanied by hallucinations that support the delusional beliefs. Delusional parasitosis with formication ("cocaine bugs") is also a fairly common symptom. Cocaine- induced psychosis shows sensitization toward the psychotic effects of the drug.
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Alternate term for organic hallucinosis and delusional parasitosis, the continuous belief that one's skin or body has been infested by parasites or insects. This state cannot be diagnosed if the hallucinatory state is produced while the individual is under the influence of drugs or alcohol, or if the individual fulfills the criterion for delirium. In general, if an individual is under the influence of a drug, or experiencing the symptoms of withdrawal from that drug, this condition is not psychiatric but medical, and termed formication.
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Drugs such as cocaine and methamphetamine, which increase the pharmacological effects of dopamine, have been shown to cause uncontrollable picking in users. These drugs can create the sensation of formication, which feels like something is crawling on or under the skin. Thus, excoriation disorder could result from a dysfunction in the dopamine reward functions. There may be another neurological explanation for excoriation disorder: individuals with the condition have less motor- inhibitory control, but show no sign of difference in cognitive flexibility, when compared to individuals without the condition.
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Formication, a type of tactile hallucination, is the feeling of imaginary insects or spiders on the skin. Tactile hallucination is the false perception of tactile sensory input that creates a hallucinatory sensation of physical contact with an imaginary object. It is caused by the faulty integration of the tactile sensory neural signals generated in the spinal cord and the thalamus and sent to the primary somatosensory cortex (SI) and secondary somatosensory cortex (SII). Tactile hallucinations are recurrent symptoms of neurological diseases such as schizophrenia, Parkinson's disease, Ekbom's syndrome and delerium tremens.
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Delusional parasitosis (DP) is a mental disorder in which individuals have a persistent belief that they are infested with living or nonliving pathogens such as parasites, insects, or bugs, when no such infestation is present. They usually report tactile hallucinations known as formication, a sensation resembling insects crawling on or under the skin. Morgellons is considered to be a self-diagnosed subtype of this condition, in which individuals have sores that they believe contain harmful fibers. Delusional parasitosis is classified as a delusional disorder in the Diagnostic and Statistical Manual of Mental Disorders (DSM5).
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The cause of delusional parasitosis is unknown. It may be related to excess dopamine in the brain's striatum, resulting from diminished dopamine transporter (DAT) function, which regulates dopamine reuptake in the brain. Evidence supporting the dopamine theory is that medications that inhibit dopamine reuptake (for example cocaine and amphetamines) are known to induce symptoms such as formication. Other conditions that also demonstrate reduced DAT functioning are known to cause secondary DP; these conditions include "schizophrenia, depression, traumatic brain injury, alcoholism, Parkinson's and Huntington's diseases, human immunodeficiency virus infection, and iron deficiency".
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In general, DT is considered the most severe manifestation of alcohol withdrawal and occurs 3–10 days following the last drink. Other common symptoms include intense perceptual disturbance such as visions of insects, snakes, or rats. These may be hallucinations or illusions related to the environment, e.g., patterns on the wallpaper or in the peripheral vision that the patient falsely perceives as a resemblance to the morphology of an insect, and are also associated with tactile hallucinations such as sensations of something crawling on the subject—a phenomenon known as formication.
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After using cocaine on a regular basis, many users will become addicted. When the drug is discontinued immediately, the user will experience what has come to be known as a "crash" along with a number of other cocaine withdrawal symptoms, including paranoia, depression, exhaustion, anxiety, itching, mood swings, irritability, fatigue, insomnia, an intense craving for more cocaine, and in some cases nausea and vomiting. Some cocaine users also report having similar symptoms to schizophrenia patients and feel that their mind is lost. Some users also report formication: a feeling of a crawling sensation on the skin also known as "coke bugs".
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Stimulant drug abuse (particularly amphetamine and cocaine) can lead to delusional parasitosis (aka Ekbom's Syndrome: a mistaken belief they are infested with parasites). For example, excessive cocaine use can lead to formication, nicknamed "cocaine bugs" or "coke bugs", where the affected people believe they have, or feel, parasites crawling under their skin. (Similar delusions may also be associated with high fever or in connection with alcohol withdrawal, sometimes accompanied by visual hallucinations of insects.) "Delusional Parasitosis", The Bohart Museum of Entomology, 2005, webpage: UCDavis-delusional. People experiencing these hallucinations might scratch themselves to the extent of serious skin damage and bleeding, especially when they are delirious.
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Gustatory, olfactory and thermal sensations in hypnagogia have all been reported, as well as tactile sensations (including those kinds classed as paresthesia or formication). Sometimes there is synesthesia; many people report seeing a flash of light or some other visual image in response to a real sound. Proprioceptive effects may be noticed, with numbness and changes in perceived body size and proportions, feelings of floating or bobbing as if their bed were a boat, and out-of-body experiences. Perhaps the most common experience of this kind is the falling sensation, and associated hypnic jerk, encountered by many people, at least occasionally, while drifting off to sleep.
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Cocaine is a powerful stimulant known to make users feel energetic, cheerful, talkative, etc. In time, negative side effects include increased body temperature, irregular or rapid heart rate, high blood pressure, increased risk of heart attacks, strokes and even sudden death from cardiac arrest. Many habitual abusers develop a transient, manic-like condition similar to amphetamine psychosis and schizophrenia, whose symptoms include aggression, severe paranoia, restlessness, confusion and tactile hallucinations; which can include the feeling of something crawling under the skin (formication), also known as "coke bugs", during binges. Users of cocaine have also reported having thoughts of suicide, unusual weight loss, trouble maintaining relationships, and an unhealthy, pale appearance.
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Common symptoms of mercury poisoning include peripheral neuropathy, presenting as paresthesia or itching, burning, pain, or even a sensation that resembles small insects crawling on or under the skin (formication); skin discoloration (pink cheeks, fingertips and toes); swelling; and desquamation (shedding or peeling of skin). Mercury irreversibly inhibits selenium-dependent enzymes (see below) and may also inactivate S-adenosyl-methionine, which is necessary for catecholamine catabolism by catechol-O-methyl transferase. Due to the body's inability to degrade catecholamines (e.g. epinephrine), a person suffering from mercury poisoning may experience profuse sweating, tachycardia (persistently faster-than-normal heart beat), increased salivation, and hypertension (high blood pressure).
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Delusional infestation is classified as a delusional disorder of the somatic subtype in the Diagnostic and Statistical Manual of Mental Disorders (DSM5). The name delusional parasitosis has been the most common name since 2015, but the condition has also been called delusional infestation, delusory parasitosis, delusional ectoparasitosis, psychogenic parasitosis, Ekbom syndrome, dermatophobia, parasitophobia, formication and "cocaine bugs". Morgellons is a form of delusional parasitosis in which people have painful skin sensations that they believe contain fibers of various kinds; its presentation is very similar to other delusional infestations, but people with this self-diagnosed condition also believe that strings or fibers are present in their skin lesions. Delusory cleptoparasitosis is a form of delusion of parasitosis where the person believes the infestation is in their dwelling, rather than on or in their body.
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People with delusional parsitosis believe that "parasites, worms, mites, bacteria, fungus" or some other living organism has infected them, and reasoning or logic will not dissuade them from this belief. Details vary among those who have the condition, though it typically manifests as a crawling and pin-pricking sensation that is most commonly described as involving perceived parasites crawling upon or burrowing into the skin, sometimes accompanied by an actual physical sensation (known as formication). Sufferers may injure themselves in attempts to be rid of the "parasites"; resulting skin damage includes excoriation, bruising and cuts, as well as damage caused from using chemical substances and obsessive cleansing routines. A "preceding event such as a bug bite, travel, sharing clothes, or contact with an infected person" is often identified by individuals with DP; such events may lead the individual to misattribute symptoms because of a more awareness of symptoms they were previously able to ignore.
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