Delusional infestation

Delusional infestation is a rare condition where a person has a firm but mistaken belief that they're infested by living organisms such as lice, fleas, worms or fungi. They complain of abnormal sensations such as itching, biting or crawling on their skin.

Delusional infestation is a mental health condition. It's called a delusion because it's difficult to convince the person that the infestation isn't real.

There are 2 types of delusional infestation – primary and secondary delusional infestation.

In primary delusional infestation, the exact cause is unknown and the person only has this condition without other associated conditions.

In secondary delusional infestation, the person has other mental health conditions or medical conditions that could be a cause, or they're taking recreational drugs or medicines that may cause delusional infestation as a side effect.

• Associated mental health conditions include depression, dementia, obsessive-compulsive disorder (OCD), bipolar disorder, post-traumatic stress disorder (PTSD), or schizophrenia.
• Medical conditions that can cause delusional infestation include hypothyroidism (low thyroid), vitamin B12 deficiency, neuropathy, diabetes and stroke.
• Recreational drug abuse including cocaine, amphetamines, and alcohol withdrawal.
• Rarely, some medicines can cause delusional infestation. These include amantadine, levodopa, topiramate, gabapentin and ropinirole.

People who have delusional infestation usually have symptoms that include:

• crawling, itching or biting sensations under their skin
• seeing organisms not seen by others people.
• skin rashes or sores that can cause intense itching
• difficulty concentrating
• depressed mood.

They may report worms or insects appearing from their nose, ears, mouth, intestines, or genitalia.

They might have reached out to the environmental health department for fumigation of their home and consulted multiple medical professionals and entomologists.

There may be evidence of the use of antiseptics, disinfectants, and insecticides.

Treatment for secondary delusional infestation includes treating any underlying conditions. 

If there’s a triggering illness, treating that illness can help ease or stop the delusional infestation.

A doctor or psychiatrist may prescribe antipsychotic medications. A person with delusional infestation may be reluctant to take these medicines because they believe their symptoms are due to an infestation rather than a mental health condition. 

If the person has been scratching due to itch, this may require treatment with emollients to calm their skin.