Signs and Symptoms of Scabies
Intense nocturnal pruritus (nighttime itching) is the hallmark feature of scabies, typically affecting all body regions except the head in adults. 1
Classic Clinical Presentation
Primary Symptom
- Severe itching that worsens at night is the defining characteristic of scabies 1, 2
- The itch typically appears out of proportion to visible skin findings 2
- With first infestation, itching may take several weeks to develop, but occurs within 24 hours after subsequent reinfestations due to sensitization to Sarcoptes scabiei 1
Skin Lesions and Distribution
- Pathognomonic burrows (serpiginous tracks up to 1 cm in length) are the definitive sign when present 3, 2
- Generalized erythematous papules and vesicles with excoriation appear across the body 3, 4
- Inflammatory changes commonly occur in intertriginous areas (skin folds) 1
Typical Body Sites Affected
- Finger webs, volar wrists, and lateral aspects of fingers 3, 4
- Axillary folds, abdomen, waist, and navel 3, 4
- Buttocks, groins, and male genitalia 3, 4
- Extensor surfaces of elbows and knees 4
- Inframammary folds in women 3
- In infants and elderly patients, the hairline, neck, temple, forehead, and scalp may be infested 1, 5
Atypical Presentations
High-Risk Populations
- Nursing home residents and debilitated patients may present with minimal or absent inflammatory changes 1
- Pruritus may be completely absent in debilitated or elderly patients 1
- Immunocompromised individuals may develop crusted (Norwegian) scabies 6, 7
Crusted Scabies Variant
- Characterized by dry, scaly, hyperkeratotic and crusted skin, particularly on extremities 2, 4
- May not be itchy despite massive mite burden (thousands to millions of mites) 6, 2
- Far more contagious than typical scabies 6
Other Clinical Variants
- Nodular scabies presents with persistent nodules 4
- Bullous scabies shows vesicular and bullous lesions 4
Diagnostic Clues from Patient History
Epidemiological Red Flags
- Symptoms in multiple family members or institutional contacts strongly suggest scabies 1
- Scabies in adults is frequently sexually acquired 1
- History of prolonged skin-to-skin contact or exposure to contaminated fomites 1
- Close contacts also experiencing itching is virtually diagnostic when combined with nocturnal pruritus 2
Critical Pitfall to Recognize
Post-Treatment Symptoms
- Persistent pruritus for up to 2 weeks after successful treatment does NOT indicate treatment failure 1, 6, 5
- Approximately 75% of patients with pruritus at 2 weeks post-treatment have complete resolution by 4 weeks 5
- Rash and itching may temporarily worsen immediately after treatment due to inflammatory response 5
- Only demonstrable living mites after 14 days indicate need for retreatment 5