Formication is the distressing sensation of insects crawling on or under the skin, often occurring as a side effect of certain drugs or during withdrawal. This feeling can be intense and persistent, frequently leading individuals to scratch or pick at their skin to remove the perceived irritants. Formication is a tactile hallucination that signals a disruption in the central nervous system’s processing of sensory information.
Defining the Sensation of Formication
Formication is a specific type of paresthesia, a term for abnormal skin sensations occurring without an apparent physical cause. The name is derived from the Latin word formica, meaning “ant,” referencing the feeling of small creatures moving across the body. This sensation is a complex, false sensory experience, distinct from a localized itch (pruritus).
Formication is classified as a tactile hallucination, where the brain generates the sensation of touch when none exists. People often describe the feeling as tingling, biting, or stinging. It can be accompanied by delusional parasitosis, a fixed, false belief that they are infested with parasites, leading to compulsive scratching and self-inflicted wounds.
Stimulants: The Primary Cause of Drug-Induced Formication
Central nervous system (CNS) stimulants are the most common pharmacological agents linked to formication. Excessive use, especially at high doses or over prolonged periods, severely disrupts the brain’s neurochemical balance. This phenomenon was first reported in chronic cocaine users in 1889, earning it the nickname “coke bugs.”
Methamphetamine use is particularly notorious for causing this symptom, frequently referred to as “meth mites.” Chronic stimulant abuse, including cocaine and methamphetamine, leads to a massive release of monoamines, especially dopamine and norepinephrine. This neurochemical hyperactivity causes a misinterpretation of sensory signals, manifesting as the feeling of crawling insects.
This dopamine dysregulation often leads to drug-induced psychosis, where formication is accompanied by the delusion of being infested. Misuse of high-dose prescription stimulants, such as amphetamines used for ADHD, can also trigger this tactile hallucination.
Formication Triggered by Withdrawal and Prescription Medications
Formication can emerge during withdrawal from depressant substances, as the central nervous system rebounds from suppression to over-activity. The most severe example occurs during alcohol withdrawal, specifically as a symptom of delirium tremens (DTs). DTs is a medical emergency occurring typically 48 to 96 hours after the last drink in severely dependent individuals, and tactile hallucinations are a recognized feature.
Prescription Medications
Several classes of therapeutic prescription medications also cause formication as a side effect. Anti-Parkinsonian agents are frequently reported because they increase dopamine levels to manage motor symptoms. Other implicated drugs include certain antidepressants (like bupropion), specific anti-seizure medications (like topiramate and levetiracetam), sedative-hypnotics, and antibiotics. In these cases, the symptom relates to the drug’s effect on neurotransmitter pathways. The onset of formication following a change in medication warrants immediate medical discussion.
Steps for Managing Drug-Related Formication
Addressing formication requires treating the underlying cause, necessitating medical intervention for proper diagnosis and management. If the symptom relates to recreational substance use, the immediate goal is safe discontinuation under professional supervision. Abrupt cessation of substances like alcohol or high-dose stimulants can lead to dangerous withdrawal syndromes, requiring medically managed detoxification.
Treatment Approaches
For cases associated with drug-induced psychosis or severe delusion, antipsychotic medications are often the primary treatment to control the tactile hallucination. Second-generation antipsychotics, such as olanzapine, may reduce the intensity of the sensation and the accompanying false belief. If formication is a side effect of a necessary prescription drug, a healthcare provider may adjust the dosage or transition the patient to an alternative.
Self-treatment is strongly discouraged, as formication can signal a serious underlying condition, such as stroke or a neurological disorder. A medical professional must rule out actual parasitic infestations or other medical causes. Symptomatic care involves topical treatments to soothe skin irritation and prevent infection from self-inflicted wounds.