Delusional infestation (DI) is a fixed, false belief that living organisms or nonliving materials infest a person’s body or environment—characterized by persistent crawling, biting, or stinging sensations—though all physical evidence indicates no such infestation. A study examining a decade of delusional infestation cases finds many sufferers endure years of distressing sensations despite no true infestation, highlighting the need for compassionate, coordinated care that addresses both medical and psychiatric factors. (Photo via iStock>

By Melissa Mayer

Melissa Mayer

The email makes me sit back in my chair. The writer details a harrowing experience: Insects infest his bed and transform into bits of wire under inspection, or they evaporate when caught. The situation is so bad and has been going on for so long that he’s starting to feel crazy.

It’s not the first such email I’d received. And I’m just a science writer.

I thought about him when I reached out to Gale Ridge, Ph.D., an entomologist and leading expert on delusional infestation, who coauthored a July 2026 Journal of Medical Entomology article with medical student Quinn Coughlin, examining 10 years of her records of delusional infestation cases at the Connecticut Agricultural Experiment Station.

A Skin-Crawling Psychiatric Disorder

Gale Ridge, Ph.D., is an associate agricultural scientist in the Department of Entomology at the Connecticut Agricultural Experiment Station and an expert in working with cases of delusional infestation. She is also a trained pianist; CAES had a formal dinner in 2025 celebrating its 150th anniversary, and Ridge served as the cocktail pianist, pictured here. (Photo courtesy of Gale Ridge, Ph.D.)

Delusional infestation (DI) is a fixed, false belief that living organisms or nonliving materials infest a person’s body or environment—characterized by persistent crawling, biting, or stinging sensations—though all physical evidence indicates no such infestation. It has also previously been referred to as “delusional parasitosis” and “Ekbom syndrome.”

The condition can occur in the absence of other psychiatric conditions or substance use or along with those. It can also involve other people, like in the case of shared DI (a folie à deux in which a delusion transmits from one person to another) and DI by proxy (in which the perceived infestation focuses on another, such as a pet or child). Ridge remembers one case that spread through an entire call center, eventually affecting 60 people.

Quinn Coughlin

“The reason it’s very difficult to treat these cases is you have two things going on simultaneously,” Ridge says. “There’s an undiagnosed underlying medical condition that’s expressing a single symptom and then the psychiatric layer on top protecting it.”

That underlying condition can be anything from an allergy to a neurological issue to the creepy-crawly sensations that can come with menopause. It’s also strongly associated with stress, both personal and societal. Ridge reports upticks in cases during the Great Recession, the COVID-19 pandemic, and the current period of sociopolitical volatility. She had 1,680 DI-related interactions just last year.

Picking Through the Data

Coughlin analyzed 264 cases of suspected delusional infestation from Ridge’s office between 2013 and 2023. He found that most patients were female with a mean age of just over 60 years. On average, symptoms lasted for more than 16 months, though a good chunk of patients experienced symptoms for more than three years. Reported symptom onset was more common in warmer months.

The most reported infestations were unspecified parasites, mites, and bed bugs. Nearly half of patients submitted specimens—mostly debris, lint, and arthropods that couldn’t cause their symptoms. That’s the “matchbox sign,” a classic clue for the illness. Another 20% submitted digital photos.

A study examining a decade of delusional infestation cases finds many sufferers endure years of distressing sensations despite no true infestation, highlighting the need for compassionate, coordinated care that addresses both medical and psychiatric factors. Entomologists at the Connecticut Agricultural Experiment Station have worked with many DI sufferers; a common sign of the condition is collection of “specimens” that are mostly debris, lint, and arthropods that couldn’t cause their symptoms. (Photo courtesy of Connecticut Agricultural Experiment Station)

A study examining a decade of delusional infestation cases finds many sufferers endure years of distressing sensations despite no true infestation, highlighting the need for compassionate, coordinated care that addresses both medical and psychiatric factors. Entomologists at the Connecticut Agricultural Experiment Station have worked with many DI sufferers; shown here is a sampling method they recommend to people wanting to submit samples in order to encourage a high-quality sample versus a high-quantity sample. (Photo courtesy of Connecticut Agricultural Experiment Station)

Finding a Path to Care

That data showed that people were most likely to treat their affliction with antiparasitics and much less likely to try antipsychotic medications, which is a mainstay treatment. Ivermectin and permethrin were the most named medications.

Delusional infestation can have severe consequences, including social isolation, housing instability, relationship strain, financial hardship and work impairment. The paper also documented suicidal ideation in five cases and psychiatric hospitalization in four. Ridge has experienced one accidental death and one suicide among the DI cases she’s encountered, driving her to approach each contact with care.

The authors say it’s difficult to coordinate treatment in a decentralized healthcare system, especially when most medical teams aren’t aware of DI—and might make the problem worse by prescribing treatment without careful investigation. Ideally, informed care teams would link medical specialists like dermatologists with psychiatrists to treat the whole patient.

For Ridge, effective treatment boils down to time and trust. She told me story after desperate story: a man sleeping in his dining room, convinced by a careless healthcare provider that his pregnant partner had given him scabies; a woman systematically removing her fingernails; a man losing his business during an economic downturn whose symptoms clear up when his family and employees rally around him.

Ridge spends hours with those who come to her, carefully inviting them to lead their own inquiry, sliding their specimens under the Zeiss scope she has set up for this purpose, and following up over time as they work through all the factors of their particular DI.

Treatment also depends on doctors willing to learn—like Coughlin.

“I think these patients really deeply want help,” he says. “They’re distressed, and I think just giving them the time gives them a sense of dignity and makes them more open to seeking out the help that will actually help them rather than writing them off.”

Melissa Mayer is a science writer and the human behind Washington State University’s science cat, Dr. Universe. Email: melissa.j.mayer@gmail.com.