Very itchy skin. Differential diagnosis

Author: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, May 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:

Acute dermatitis

Acute dermatitis

Subacute dermatitis

Subacute dermatitis

Chronic dermatitis

Chronic dermatitis

Infected dermatitis

Infected dermatitis

If clinical diagnosis of an itchy skin problem is uncertain, consider performing the following tests:

Dermatoscopic examination of hair shaft

Dermatoscopic examination of hair shaft

Dermatoscopic examination of possible burrows

Dermatoscopic examination of possible burrows

Skin biopsy for histopathology, and if available, direct immunofluorescence 

Skin biopsy for histopathology

Skin biopsy for histopathology

General treatments for itchy skin conditions may include:

Differential diagnosis

Consider:

Very itchy skin with localised rash   

  1. Contact dermatitis 
Contact dermatitis

Contact dermatitis

Head lice

Head lice

Insect bites

Insect bites

Lichen planus

Lichen planus

Lichen sclerosus

Lichen sclerosus

Lichen simplex

Lichen simplex

Dyshidrotic eczema

Dyshidrotic eczema

Venous dermatitis

Venous dermatitis

Mildly itch skin with localised rash  

Asteatotic eczema

Asteatotic eczema

Psoriasis

Psoriasis

Seborrhoeic dermatitis

Seborrhoeic dermatitis

Very itchy skin with generalised rash

Autoeczematisation

Autoeczematisation

Bullous pemphigoid

Bullous pemphigoid

Dermatitis herpetiformis

Dermatitis herpetiformis

Eczema

Eczema

Discoid eczema

Discoid eczema

Erythroderma

Erythroderma

Lichen planus

Lichen planus

T-cell lymphoma

T-cell lymphoma

Neurodermatitis

Neurodermatitis

Nodular prurigo

Nodular prurigo

Scabies

Scabies

Transient acantholytic dermatosis

Transient acantholytic dermatosis

Urticaria

Urticaria

Mildly itchy skin with generalised rash

Psoriasis

Psoriasis

Xerotic eczema

Xerotic eczema

Localised itchy skin without rash

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.

Excoriations

Excoriations

Lichen simplex

Lichen simplex

Lichen simplex

Lichen simplex

Generalised itchy skin without rash

Examine carefully for scabetic burrows.

Pruritus of pregnancy

Pruritus of pregnancy

 

Chronic renal insufficiency

Chronic renal insufficiency

Unknown origin

Unknown origin

 

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Watch Dr Amanda Oakley presenting "Skin lesion photography" at The Australasian Skin Cancer Congress.

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