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Home Topics A–Z The differential diagnosis of itchy skin
Author: A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, February 2016.
Itch is defined by a desire to scratch.
An acute or chronic itchy rash is most often due to dermatitis/eczema. Dermatitis can be primary, or secondary to scratching.
Stages include:
Stages of dermatitis
General treatments for itchy skin conditions may include:
Contact dermatitis
Insect bites / papular urticaria
Insect bites
Lichen planus
Lichen sclerosus
Lichen simplex
Pompholyx (dyshidrotic eczema)
Pompholyx
Venous eczema
Venous eczema
Psoriasis
Seborrhoeic dermatitis
Autoeczematisation
Bullous pemphigoid
Dermatitis herpetiformis
Atopic dermatitis (eczema)
Discoid eczema
Erythroderma
Lichen planus
Mycosis fungoides (cutaneous T-cell lymphoma)
Mycosis fungoides
Neurodermatitis
Nodular prurigo
Scabies
Transient acantholytic dermatosis / Grover disease
Transient acantholytic dermatosis
Urticaria
Psoriasis
Xerosis (dry skin)
May have secondary lesions due to scratching: erosions, purpura, lichen simplex and secondary infection. Localised itch is often neuropathic/neurogenic. If scalp itchy, look carefully for head lice and their egg cases.
Localised neuropathic itch
Examine carefully for scabietic burrows.
Systemic disease
Systemic associations with generalised pruritus
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