Delusional parasitosis is a rare psychiatric condition in which a person mistakenly thinks that they have a parasitic infestation. They believe that lice, fleas, worms, mites, or other organisms have entered their body and overtaken their surroundings.

Although doctors find no medical evidence of an infection or infestation, the person with the delusion can often describe how the bugs enter their body and move around. They experience realistic irritation and other sensations, and they may pick at their skin enough to cause open wounds.

Doctors may also refer to delusional parasitosis as delusional infestation or Ekbom syndrome. It has a close association with Morgellons disease, where someone strongly believes that they have fibers or threads coming out of their skin. Morgellons disease is controversial, as some doctors consider it a psychiatric condition, whereas others believe that skin cells or other cells create the fibers.

This article looks at delusional parasitosis in more detail, including its types, symptoms, and causes. It also discusses the diagnosis and treatment of this condition and the outlook for someone living with it.

there is a black and white photo of a person scratching their shoulderShare on Pinterest
Daniel Nery/EyeEm/Getty Images

Doctors will classify delusional parasitosis as one of three subtypes:

  • Primary delusional parasitosis: People with primary delusional parasitosis believe that they are experiencing a parasitic infestation with an insect or another organism. Someone with this type of delusional parasitosis has no other symptoms.
  • Secondary delusional parasitosis: A person with this subtype also experiences other psychiatric disorders, such as anxiety, depression, schizophrenia, paranoia, dementia, or a phobia.
  • Organic delusional parasitosis: Research has linked this type of delusional parasitosis with various health conditions, including diabetes, hyperthyroidism, anemia, hepatitis, nutritional deficiencies, central nervous system infections, and drug abuse.

The major symptom of delusional parasitosis is a person having a strong and unwavering belief that parasites have infected them. The affected individual thinks that they have parasites crawling inside their body or on their skin, but doctors can find no evidence of the infestation.

A person with delusional parasitosis may also believe that parasites have infested their home or belongings. Sometimes, people may bring what they consider physical evidence to show their healthcare provider. Doctors call this the matchbox sign.

Other reported symptoms may include:

  • itching
  • burning sensation
  • feelings of being bitten
  • numbness
  • a crawling or prickling sensation in the skin

A person may attempt to treat the condition. For example, they may try:

  • picking or scratching at their skin
  • self-mutilating to dig out the parasites
  • scrubbing at their skin
  • using bleach or other strong chemicals on their skin to kill the supposed parasites

According to the American Osteopathic College of Dermatology, people experiencing delusional parasitosis usually do not have unusual personality traits and display no signs of any systemic illnesses. However, an underlying illness can cause organic delusional parasitosis.

Doctors do not fully understand why some people experience delusional parasitosis. It is most common in middle-aged women, although it can affect anyone regardless of age, sex, gender, or race.

Some cases link to other conditions that create a chemical imbalance in the brain. As a result, researchers think that abnormal levels of dopamine can contribute to delusional parasitosis. In addition, the misuse of drugs can also cause the itching, crawling sensation that people experience with delusional parasitosis.

Sometimes, a close relative may also share the belief that an individual has a parasitic infestation. Doctors call this folie à deux.

If an underlying health condition causes delusional parasitosis, treatment for the condition could ease the symptoms.

It can be challenging for doctors to treat delusional parasitosis, as affected individuals strongly believe that they have a parasitic infestation rather than a psychiatric condition. Due to this, they are less likely to respond positively to psychiatric medications.

According to some research, it is usually easier for people to accept treatment when a dermatologist rather than a psychiatrist prescribes it because of the stigma surrounding mental health issues. So, potentially, a dermatologist could prescribe medication to treat the distress and itching.

However, some healthcare professionals may not know what the appropriate treatment is for this condition and may prefer to refer the individual to a psychiatrist. The psychiatrist and dermatologist may benefit by working together to build a relationship with the person before starting their treatment.

Doctors might prescribe antipsychotic medications for people experiencing delusional parasitosis. These may include:

  • aripiprazole (Abilify)
  • olanzapine (Zyprexa)
  • pimozide (Orap)
  • risperidone (Risperdal)

It is important that people do not trick the individual into taking an antipsychotic medication by telling them that it will treat the supposed parasites. Instead of helping, this will strengthen their conviction about the parasites and make it more difficult to treat their condition in the future.

To diagnose delusional parasitosis, doctors must first rule out any other conditions. Usually, an individual visits a dermatologist or their primary care physician (PCP) to treat the perceived infestation. Therefore, the first step is for the healthcare provider to rule out an actual infestation. They can examine the person’s skin and hair under a microscope to rule out scabies and lice infestations.

A doctor may then order blood tests to rule out any other medical causes of the itchy skin or other symptoms relating to delusional parasitosis. Possible medical causes include:

  • hepatitis
  • HIV
  • infection
  • dermatitis herpetiformis
  • thyroid disease
  • anemia
  • renal dysfunction
  • neurologic dysfunction
  • lymphoma

It is also essential to determine whether someone experiencing delusional parasitosis has a history of drug use, specifically amphetamines, methylphenidate, or cocaine, as these drugs can cause delusions.

Delusional parasitosis is a psychiatric condition. Although the symptoms rarely affect a person’s ability to function, the delusions can decrease a person’s quality of life if they do not receive treatment.

Some people may find that reassurance and support from their healthcare team is enough to allow them to manage their symptoms, but others may require therapy or psychiatric medication.

No single treatment is suitable for all people with delusional parasitosis. However, the right treatment or combination of treatments for an individual may ease their symptoms or cure them completely.

With folie à deux, which occurs in about 5–15% of cases of delusional parasitosis, the family member’s conviction in the infestation usually weakens after treatment is successful.

Anyone who thinks that they have some form of parasitic infestation should first visit their PCP to rule out any potential causes. Alternatively, they could visit a dermatologist to check whether they have any physical skin conditions.

However, the individual may need psychiatric evaluation and require treatment with medications.

Delusional parasitosis is a rare psychiatric disorder in which someone mistakenly believes that they have a parasitic infestation. It can cause great distress to those affected and their loved ones.

Healthcare professionals may need to address the condition carefully and gain the person’s trust before any treatment can effectively address their symptoms.

With appropriate treatment, people can manage the symptoms of delusional parasitosis, which may disappear in time.