What is the treatment for formication?

Treatment for Formication

Formication should be treated by addressing the underlying cause, with antipsychotic medications being the first-line treatment when associated with delusional infestation or psychosis.

Understanding Formication

Formication is a tactile hallucination characterized by sensations of insects crawling, stinging, or biting on or under the skin without any actual infestation. It's important to distinguish this from actual infestations or other skin conditions.

Common Causes of Formication

1. Substance-Related Causes:

   • Recreational drugs (cocaine, amphetamines, cannabis) 1, 2, 3
   • Prescription medications (anti-Parkinsonian agents, antidepressants, prescription stimulants, propranolol, antiepileptics) 1
   • Alcohol withdrawal
   • Lead toxicity 4

2. Psychiatric Conditions:

   • Delusional infestation (previously called delusional parasitosis) 1, 3
   • Monosymptomatic hypochondriacal psychosis 1
   • Other psychotic disorders

3. Medical Conditions:

   • Perineural involvement of skin cancers 5
   • Peripheral neuropathy
   • Menopause (hormonal changes)
   • Diabetes

Diagnostic Approach

• Thorough skin examination to rule out actual infestations or dermatological conditions
• Drug screening when presentation includes chronic skin lesions, vague medical history, negative findings from previous evaluations, labile affect, and delusional behavior 2
• Evaluation for underlying medical conditions that could cause neuropathic symptoms
• Psychiatric assessment when delusional thinking is present

Treatment Algorithm

Step 1: Identify and Address Underlying Causes

• If drug-induced: Discontinue or modify the causative medication/substance 1

  • For recreational drug use: Consider addiction treatment referral 3
  • For lead toxicity: Chelation therapy 4

• If associated with skin cancer: Evaluate for perineural involvement and consider radiation therapy 5

Step 2: Pharmacological Management

• For primary psychiatric causes (delusional infestation, psychosis):

  • First-line: Antipsychotic medications
  • Second-line: Consider augmentation with SSRIs if comorbid depression/anxiety exists

• For neuropathic symptoms (when no psychiatric component):

  • Gabapentin or pregabalin
  • Topical lidocaine
  • Tricyclic antidepressants (amitriptyline, nortriptyline)

Step 3: Symptomatic Management of Skin

• Topical treatments to reduce irritation:
  • Emollients (50% white soft paraffin with 50% liquid paraffin) 6
  • Consider mild topical corticosteroids for inflammation
  • Avoid preparations containing sensitizers or irritants

Step 4: Therapeutic Alliance and Follow-up

• Establish trust with the patient
• Avoid directly contradicting delusional beliefs
• Regular follow-up to monitor response to treatment
• Consider dermatology-psychiatry collaborative care

Special Considerations

• High suspicion of recreational drug use: In patients with delusional infestation, up to 33.3% may test positive for recreational drugs even when not initially disclosed 3

• Elderly patients: Consider medication side effects as a common cause

• Patients with skin lesions: Self-inflicted excoriations from scratching require wound care and infection prevention

Pitfalls to Avoid

• Dismissing symptoms as "just psychological"
• Failing to screen for substance use
• Missing underlying medical conditions like skin cancer with perineural involvement
• Prescribing antibiotics or antiparasitics when no infestation exists
• Reinforcing delusional beliefs by excessive testing for parasites

By systematically addressing the underlying causes of formication while providing symptomatic relief, most patients can experience significant improvement in their symptoms and quality of life.