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Delusions of parasitosis

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Delusions of parasitosis

What is delusions of parasitosis?

Delusions of parasitosis is a rare and very distressing psychiatric disorder. The person suffering from the condition truly believes that their skin is infested by parasites (mites, lice or other insects). However, when the skin is examined, no parasites or bugs can be seen in or on the skin.

The person will often experience sensations of biting, crawling and stinging related to the false belief or delusion and refuses to believe that the parasites are not there. However, when interacting and talking about other aspects of their life, their behavior and functionality is completely normal.

The psychiatric disorder must be differentiated from other conditions that may lead to abnormal sensations in the skin, (e.g. effects of cocaine or amphetamine addiction or due to a medical cause such as vitamin B12 deficiency).

What causes delusions of parasitosis?

The cause of delusions of parasitosis is unknown.

What does delusions of parasitosis look like?

Typically, those affected with the condition have consulted many doctors over many months or years, but have never had any success in eradicating the belief that their skin is infested with parasites.

Affected people often bring specimens picked from their skin for examination, believing them to be bugs or parts of bugs. However, these specimens are usually scabs or cloth fibres and do not include parasites. Individuals often give extensive descriptions of the bugs’ appearance, habitat, reproductive cycle as well as where these enter and leave their body.  Affected individuals may have had repeated exterminators in their homes and sprayed themselves and their homes with potentially toxic pesticides.

The skin changes seen are those that have been caused by scratching, picking and digging into the skin to get the bugs out. They may also have dermatitis related to the various creams, disinfectants and toxic chemicals that have been used repeatedly on their skin, again in the false belief that they are killing the bugs.

There may be little to find on the skin which makes it very important to eliminate any other possible cause of the crawling, stinging biting sensations.

What other problems can occur with delusions of parasitosis?

  • If delusions of parasitosis is not treated, scarring can result because of the repeated and persistent self-inflicted trauma to the skin.
  • The person’s entire life and family may be disrupted by their distress and attempts at treatment.
  • Frequently the person does not accept that the problem is psychiatric and may refuse to see a psychiatrist. In this case the dermatologist may have to prescribe the appropriate antipsychotic medication to suppress the symptoms. These medications have a number of side effects that need to be carefully monitored.

How is delusions of parasitosis diagnosed?

A dermatologist usually makes the diagnosis from a thorough medical history and careful skin examination plus a microscopic examination of samples brought along by the affected person. The dermatologist must exclude other medical conditions, illicit drug use or psychiatric problems that could be contributing or causing this condition. Blood tests or skin scrapings may be needed to exclude other conditions.

How is delusions of parasitosis treated?

Delusions of parasitosis can be very difficult to treat.  The majority of cases require treatment with oral medications known as antipsychotics (most commonly risperidone or olanzapine). The affected person is usually reluctant to seek psychiatric care or to accept a referral to a psychiatrist. A multidisciplinary team approach is needed which involves the dermatologist liaising with the psychiatrist and the GP.

What is the likely outcome of delusions of parasitosis?

The most difficult aspect of treatment is convincing the person suffering from this condition that the infestation is not real and that they need antipsychotic medications. This condition can persist for many years and frequently relapses when treatment is stopped.

This information has been written by Dr Sophie Bakis-Petsoglou
Updated 30 June 2015

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