Itch without a primary rash
A structured differential for generalised pruritus when only scratch marks are visible.
Updated: 2026-09-13
Written for clinicians and medical students
This section is a teaching reference for doctors, residents and medical students. It is not patient guidance and not a substitute for clinical examination, and it must not be used for self treatment.
Clinical sorting
- First exclude subtle scabies, urticaria, xerosis, dermatitis and bullous pemphigoid. Examine finger webs, genital skin, scalp, nails and mucosa [1].
- Ask about new medicines, pregnancy, renal or liver disease, thyroid symptoms, weight loss, fever, night sweats and affected contacts.
- Neuropathic itch is often localised with dysaesthesia; psychogenic itch is a diagnosis requiring positive features and exclusion of medical causes, not an assumption.
Initial investigations
- When generalised itch persists without explanation, consider full blood count, ferritin, renal and liver profile, thyroid testing, glucose and other tests directed by history and examination [1].
- Investigate red flags such as lymphadenopathy, organomegaly, constitutional symptoms or abnormal examination urgently. Avoid indiscriminate tumour-marker screening.
- Skin biopsy with direct immunofluorescence and pemphigoid serology can identify prebullous pemphigoid in the appropriate older patient.