Why do patients with anxiety experience pruritus or formication (the sensation of bugs crawling on the skin)?

Why Anxiety Causes Itching and Formication

Anxiety triggers pruritus and formication (the sensation of bugs crawling on the skin) through direct activation of neural circuits in the hippocampus and subcortical brain structures, which release stress mediators—including nerve growth factor, corticotropin-releasing hormone, and substance P—that lower the itch threshold, increase sensory nerve density, and perpetuate neurogenic inflammation in the skin. 1, 2

The Brain-Skin Connection: Neurobiological Mechanisms

Central Nervous System Pathways

• Stress activates specific brain regions that process both emotion and itch sensation, particularly the limbic system (which governs emotional responses) and the periaqueductal gray (which facilitates descending itch signals), creating a direct pathway from psychological distress to cutaneous symptoms. 3

• The hypothalamic-pituitary-adrenal (HPA) axis and sympathetic nervous system become activated during anxiety, triggering a cascade of stress hormones and neuropeptides that directly stimulate itch-sensing nerve fibers in the skin. 1, 2, 3

• Visual and verbal suggestion alone can elicit pruritus, demonstrating that the central nervous system can generate itch sensations independent of any peripheral skin pathology—this explains why anxious patients may experience formication even when no physical cause exists. 4

Peripheral Mechanisms in the Skin

• Stress mediators released systemically and locally in the skin—including nerve growth factor, substance P, acetylcholine, histamine, and inflammatory cytokines—increase the density of sensory nerve endings, upregulate production of other itch-inducing agents, and perpetuate neurogenic inflammation. 2, 3

• Mast cells serve as "central cellular switchboards" that respond to stress signals by releasing histamine and other pruritogenic mediators, even in the absence of allergic triggers. 2

• Keratinocytes (skin cells) also respond to stress hormones by secreting additional itch-promoting substances, creating a local inflammatory environment that amplifies itch perception. 3

The Vicious Cycle: Why Anxiety and Itch Perpetuate Each Other

• Chronic itch increases stress, anxiety, and depression, which in turn exacerbate itch intensity, creating a self-reinforcing cycle that persists across all chronic itch conditions regardless of their original cause. 5

• Negative emotions—including rage, fear, annoyance, and embarrassment—can directly trigger or worsen itching through activation of the same neural pathways, explaining why anxious rumination intensifies formication. 4

• This cycle significantly impairs quality of life in a manner comparable to chronic pain, with common consequences including disrupted sleep, feelings of stigmatization, distorted body image, and development of anxiety or depressive disorders in up to 33% of patients. 1, 4

• Even minor daily stressors contribute to symptom development, not just major life events, meaning that ongoing anxiety maintains the itch-scratch cycle. 1

Diagnostic Criteria for Functional (Psychogenic) Itch

Before attributing itch to anxiety, you must exclude all physical causes through comprehensive laboratory evaluation. 1

Compulsory Criteria (All Three Must Be Present)

• Chronic pruritus lasting >6 weeks. 1, 4
• No identifiable somatic cause after thorough investigation (see workup below). 1, 4
• Variations in intensity associated with stress or psychological factors. 1

Optional Criteria (At Least Three of Seven Support the Diagnosis)

• Chronological relationship with stressful life events. 1, 4
• Worsening at night. 1, 4
• Predominance during rest or inaction. 1, 4
• Associated psychological disorder (anxiety, depression, OCD). 1, 4
• Improvement with psychotropic drugs or psychological therapy. 1, 4

Essential Workup to Exclude Physical Causes

Never diagnose psychogenic pruritus without this comprehensive evaluation: 1

• Complete blood count with differential (to screen for lymphoma, polycythemia vera, anemia). 6
• Comprehensive iron studies (serum iron, ferritin, transferrin saturation)—ferritin alone is insufficient because it can be falsely normal in inflammatory states; iron deficiency accounts for 25% of generalized pruritus cases and resolves completely with replacement. 6
• Liver function tests, total bilirubin, and serum bile acids (cholestatic liver disease causes severe pruritus). 6
• Renal panel (urea, creatinine, electrolytes) to detect uremic pruritus. 6
• Thyroid function tests if clinical features suggest thyroid disease. 6
• Comprehensive metabolic panel to exclude systemic disease. 1
• Medication review (drug-induced pruritus accounts for 12.5% of cases). 6

Treatment Algorithm for Anxiety-Related Pruritus

First-Line: Psychosocial and Behavioral Interventions

The British Association of Dermatologists recommends psychosocial and behavioral interventions as primary treatment for stress-related pruritus: 1

• Education on trigger factor avoidance—identifying and minimizing anxiety-provoking situations that precipitate itch. 1, 4

• Relaxation techniques (progressive muscle relaxation, deep breathing exercises, meditation) to reduce HPA axis activation. 1, 4

• Cognitive restructuring to address catastrophizing thoughts about itch and formication. 1, 4

• Habit-reversal training—substituting scratching with alternative behaviors such as fist-clenching, applying pressure, or using ice packs. 6

• "Coping with Itch" programs have demonstrated significant improvements in itch-related coping, reduced catastrophizing thoughts, and decreased healthcare utilization by 27%, though they do not reduce itch intensity itself. 1, 4

Adjunctive Pharmacological Treatments

• Topical moderate-to-high potency corticosteroids for symptomatic relief of any secondary skin changes from scratching. 1

• Second-generation non-sedating antihistamines (fexofenadine 180 mg or loratadine 10 mg daily) provide modest symptomatic relief while behavioral interventions take effect. 1, 6

• Gabapentin 300–1200 mg daily is effective for neuropathic components of anxiety-related itch, particularly when formication is prominent. 7, 6

• Psychotropic medications targeting the underlying anxiety disorder—SSRIs (paroxetine, sertraline), SNRIs (duloxetine), or mirtazapine—address both the psychiatric condition and the itch through central nervous system modulation. 6, 3

When to Refer

• Dermatology referral if pruritus persists >2–4 weeks despite first-line therapy or if diagnostic uncertainty remains. 6

• Psychiatry or psychology referral for formal cognitive-behavioral therapy, especially when anxiety disorder is severe or when patients have difficulty implementing self-directed behavioral interventions. 1, 4

Critical Pitfalls to Avoid

• Never diagnose psychogenic pruritus without comprehensive laboratory evaluation—missing iron deficiency, thyroid disease, or early cholestatic liver disease is a common and preventable error. 1, 6

• Do not rely on antihistamines alone for anxiety-related itch; they are generally ineffective for centrally-mediated pruritus and must be combined with behavioral interventions. 6

• Avoid long-term sedating antihistamines (hydroxyzine, diphenhydramine) due to increased dementia risk, particularly in elderly patients. 6

• Recognize that the itch-anxiety cycle is self-perpetuating—treating only the itch without addressing the underlying anxiety, or vice versa, will result in treatment failure. 5

• Acknowledge that formication is a real neurological phenomenon, not a delusion—patients experience genuine sensory input generated by stress-activated neural circuits, and dismissing their symptoms worsens psychological distress. 4, 2