Delusional Parasitosis Can Make People Think They Have Parasites—What to Know About the Psychiatric Condition

When you visit a health care professional for a potential illness, you expect that they'll be able to make things better—and hopefully quickly. But in the case of delusional parasitosis, that can be a difficult thing to do.

When someone has this mental health condition, they mistakenly believe that they have a parasite. It can be a confusing and frustrating process for both the patient and doctors, clinical psychologist Thea Gallagher, PsyD, an assistant professor at NYU Langone Health and co-host of the Mind in View mental health-focused podcast, tells Health. "It feels very real to the patient," she says.

But what is delusional parasitosis, and what are the signs that someone has this condition vs an actual parasitic infection? Here's what you need to know.

What is delusional parasitosis?

Delusional parasitosis is a rare disorder where patients have "the false and persistent belief" that they are infected with parasites (like mites and lice), worms, insects, bacteria, or other small living organisms, according to the American Psychological Association (APA).

"Individuals will often have this sensation that they have some sort of parasitic infection," Keith Stowell, MD, chief medical officer for Rutgers University Behavioral Health Care, tells Health. "It can feel like something has crawled under their skin or is embedded in their hair—it manifests in different ways."

Dr. Stowell lists the following as potential physical and mental behaviors associated with the condition:

• Feeling like you have a parasite on or inside your skin
• Bringing in objects such as hair, lint, or skin to try to "prove" they have an infestation, despite none being found
• Damaging or removing part of their skin or applying toxic items to the skin to try to get rid of the "parasite"

"People actually feel like they have itchiness, pain, or like something is crawling on or under their skin," Dr. Stowell says. All of this can lead to complications like skin irritation and emotional distress, Gallagher says.

Why do people develop delusional parasitosis?

It's not entirely clear. "If someone is presenting with these symptoms, [it may be] an indication that they are struggling with a severe and persistent mental illness," Gallagher says. For example, paranoid delusions like those brought on by delusional parasitosis can be a sign of another mental health disorder, like schizophrenia or psychosis, she says. (Psychosis, in case you're not familiar with it, is a mental health disorder in which someone is disconnected from reality, per the National Institute of Mental Health.)

The APA also notes that the delusional parasitosis may happen "in isolation" (meaning, on its own) or alongside health conditions like diabetes or hypothyroidism.

How is delusional parasitosis diagnosed?

Because people with delusional parasitosis believe that they're infested with a parasite, they'll usually seek care at their doctor's office or ER, Dr. Stowell says. "They will not usually come to a mental health provider," he adds.

Because it's "quite possible that there may physically be something going on," doctors will generally do an initial workup to see if they can, in fact, find a parasite, Dr. Stowell says. "To folks with delusional parasitosis, this is very real," he adds. If doctors don't find anything, they'll send the patient home. It's only when the patient keeps coming back and insisting that they have a parasite—despite medical evidence to the contrary—that doctors start to suspect delusional parasitosis.

If a patient goes to their doctor about the suspected parasites several times, doctors will typically try to bring in a mental health professional to make an actual diagnosis, Gallagher says.

To be diagnosed with delusional parasitosis, patients must believe that they're infected with a parasite or other bug after repeatedly being told they aren't, Gallagher says. So if you're worried you have a parasite, you seek medical care, are told you don't have an infection, and you believe that diagnosis, that's not really grounds for delusional parasitosis.

How is delusional parasitosis treated?

It can be tricky to treat, given that people with delusional parasitosis actually believe that they have a parasite, Gallagher says. However, if patients are willing, they will often be given an anti-psychotic medication like olanzapine. "It can work quite well," Dr. Stowell says. Cognitive behavioral therapy, a form of talk therapy that aims change the way a person views a situation or stressor, may also help to "restructure" a person's delusions.

Unfortunately, delusional parasitosis is a difficult condition to treat. "A lot of individual do not view this as a psychiatric issue, so they're unwilling to accept psychiatric treatment for it," Dr. Stowell says.

Overall, Dr. Stowell says, there's still a lot doctors don't know about delusional parasitosis. "There are a relatively sparse number of cases," he says. "When they do occur, it's not like we usually have the option to research these patients."