Case 31: A woman who brings the “parasites” from her scalp

Case 31: A woman who brings the “parasites” from her scalp

A 61-year-old woman, sent by the dermatologists, who is sure she has parasites under the skin of her scalp and brings bits of skin to prove it.

  • 2 min read
  • Checked 01 Nov 2026

The case

A 61-year-old woman is referred for a psychiatric opinion by the dermatology clinic. She has seen dermatologists many times, complaining of parasites under the skin of her head and asking for a diagnosis and treatment. Examination finds raw patches where she has scratched away the surface of the skin, but no parasites. When her account is questioned, she "proves" it by scratching off pieces of her scalp, which she calls the "worms" she has been infected with.

Summary

Diagnosis

Delusional disorder, somatic type: delusional infestation, also called delusional parasitosis or Ekbom syndrome.

What points to it

  • A lasting, single delusion, through many visits (ICD-11 asks for at least three months): she is infested with parasites, with no sign of them on examination.
  • She acts to prove it: repeated visits, and the "specimens" of skin she brings (the specimen sign).
  • No other psychotic symptoms and no change in mood.

What else it could be

Rule out a real infestation such as scabies or lice, and look for what can cause the belief: drugs (stimulants, dopamine agonists), alcohol, iron deficiency, low B12 or folate, thyroid, kidney and liver disease, diabetes, and early dementia at her age. It can also be part of schizophrenia or a depression with psychotic features.

Management

  • A trusting relationship first: take the itch and the skin damage seriously, do not argue with the belief and do not confirm it. A joint dermatology and psychiatry clinic, where one exists, makes it easier for her to accept care.
  • Treat the skin: wound care, and antibiotics if it is infected.
  • A low dose of a second-generation antipsychotic, such as risperidone or olanzapine, which can be offered as a help for the itch and the distress even without insight. These are preferred at her age because they are better tolerated, which matters for adherence.
  • Pimozide, once the favourite here, is no longer preferred: no antipsychotic has proved better than the others, and pimozide lengthens the QT interval and needs ECG monitoring.

Outlook

Often chronic, but about half of those who take an antipsychotic respond well, and most improve to some degree.