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					Itchy rashes
Maggie Kirkup SpR Dermatology Royal United Hospital Bath

How common is skin disease in the population?
1. Questionnaire - 1217 unselected adults Skin accounted for 25% of 6009 ailments
(Market Research Group 1982)

2. Examination - 55% of population had a skin complaint, 22.5% worthy of medical attention1.
1Rea et al Br J Prev Soc Med 1976; 30: 107-14

Describe itch
• “local discomfort or irritation of the skin, prompting the sufferer to scratch or rub the affected area. It is the main symptom of skin disease” • “a peculiar tingling or uneasy irritation of the skin that causes a desire to scratch the affected area”

“It feels as though every nerve ending in my body is attacking me intensely at my ankles, feet, lower legs, neck, under the breasts (even the nipples tingle). It's absolutely horrendous! My hands grow red as a beet and the itching nearly takes the skin off my hands as I scratch.”
All Party Parliamentary Report on Impact of Skin Disease. 2003

“ It’s like someone tickling you under the skin”

Pathophysiology
• Debate continues over whether there are specific nerve endings for itch • Possibly more than one mechanism

Pathophysiology of itch
• Free nerve endings Fibres most concentrated in wrists and ankles Unmyelinated C fibres to dorsal horn in spinal cord • Scratching is a spinal reflex response Ascends to cerebral cortex via spinothalamic tract • Skin inflammation • Chemical mediators Substance P Opioid and non-opioid peptides Somatostatin Neurokinin A Histamine Serotonin Prostaglandins • External mediators Environmental heat or dryness

• Psychological concerns

Approach to diagnosis of itching
• History including onset, duration, pattern, effect on sleep, previous skin disease, contacts, other medical problems, drugs, response to treatment so far. • Skin examination features of rash, post-inflammatory changes, signs of scratching • General examination

Signs of itching
• • • • • • distress excoriation lichenification shiny nails weals nodules

Factors affecting presentation of itchy condition
• • • • • • age self-control/ social setting/ distractions other medical conditions/ ability to scratch site of itch specific skin condition duration

Causes of itch
• • • • • skin disorders systemic disorders psychogenic habit / itch-scratch cycle physiological?

Causes of itch
• • • • • skin disorders systemic disorders psychogenic habit / itch-scratch physiological?

Common itchy skin disorders in the young

Common itchy skin disorders in the young
• • • • • • • infestations: scabies, lice, threadworms eczemas urticaria psoriasis (sometimes) insect bites – papular urticaria pityriasis rosea viral exanthems

Common itchy skin disorders in the young
• • • • • • • infestations: scabies, lice, threadworms eczemas urticaria psoriasis (sometimes) insect bites – papular urticaria pityriasis rosea viral exanthems

Common itchy skin disorders in the young
• • • • • • • infestations: scabies, lice, threadworms eczemas urticaria psoriasis (sometimes) insect bites – papular urticaria pityriasis rosea viral exanthems

Common itchy skin disorders in the young
• • • • • • • infestations: scabies, lice, threadworms eczemas urticaria psoriasis (sometimes) insect bites – papular urticaria pityriasis rosea viral exanthems

Common itchy skin disorders in the young
• • • • • • • infestations: scabies, lice, threadworms eczemas urticaria psoriasis (sometimes) insect bites – papular urticaria pityriasis rosea viral exanthems

Common itchy skin disorders in the young
• • • • • • • infestations: scabies, lice, threadworms eczemas urticaria psoriasis insect bites – papular urticaria pityriasis rosea viral exanthems

Common itchy skin disorders in the young
• • • • • • • infestations: scabies, lice, threadworms eczemas urticaria psoriasis (sometimes) insect bites – papular urticaria pityriasis rosea viral exanthems

Common itchy skin disorders in mature adults

Common itchy skin disorders in mature adults
• • • • • • • infestations: scabies eczemas / nodular prurigo/ xerosis urticaria psoriasis (sometimes) lichen planus bullous pemphigoid polymorphic light eruption

Common itchy skin disorders in adults
• • • • • • • infestations: scabies eczemas / nodular prurigo/ xerosis urticaria psoriasis (sometimes) lichen planus bullous pemphigoid polymorphic light eruption

Common itchy skin disorders in adults
• • • • • • • infestations: scabies eczemas / nodular prurigo/ xerosis urticaria psoriasis (sometimes) lichen planus bullous pemphigoid polymorphic light eruption

Common itchy skin disorders in adults
• • • • • • • infestations: scabies eczemas /nodular prurigo/ xerosis urticaria psoriasis (sometimes) lichen planus bullous pemphigoid polymorphic light eruption

Common itchy skin disorders in adults
• • • • • • • infestations: scabies eczemas/ nodular prurigo/ xerosis urticaria psoriasis (sometimes) lichen planus bullous pemphigoid polymorphic light eruption

Common itchy skin disorders in adults
• • • • • • • eczemas / nodular prurigo/ xerosis urticaria psoriasis (sometimes) infestations: scabies lichen planus bullous pemphigoid polymorphic light eruption

Less common skin complaints which itch
• dermatitis herpetiformis • aquagenic pruritus • T cell lymphomas • pityriasis rubra pilaris • onchocerciasis etc etc

Localised itch
• Anogenital/ pruritus ani: think of threadworms, lichen sclerosis, lice, scabies, contact dermatitis
• Hands: eczemas, scabies, contact dermatitis

Localised itch
• Anogenital/ pruritus ani: think of threadworms, lichen sclerosis, lice, contact dermatitis
• Hands: eczemas, scabies, contact dermatitis

Localised itch
• Flexures: atopic/ seborrhoeic eczema, scabies • Scalp: lice, seborrhoeic dermatitis, psoriasis
• Any area: discoid eczema, lichen simplex chronicus, contact dermatitis

Less common causes of localised itch
• brachioradial pruritus

• notalgia paraesthetica

Skin disorders which don’t (usually) itch
• • • • • psoriasis ? acne/ folliculitis vasculitis/purpura erythema multiforme secondary syphilis

Causes of itch
• • • • • skin disorders systemic disorders psychogenic habit physiological?

Systemic causes of itch
• • • • liver disease renal failure iron deficiency metabolic: protein, zinc, calcium, vitamin deficiencies • thyroid disease

Systemic causes of itch (part 2)
• diabetes • malignancies: lymphoma, PRV, leukaemias, myeloma • pregnancy • neurological • drugs

Screening investigations in itchy patients with no rash
• • • • • • Full blood count Ferritin Renal function Liver function Thyroid function ? Chest X ray

Psychogenic itch
• epidemic forms - hysteria • delusional parasitosis • habit - itch/scratch cycle

Management of itching
• Treat the cause • Treat the itch

Management of itching
• There is no specific drug for itch

Management of itching
• keep looking for a cause
• avoid aggravating factors
temperature, humidity, bedding, clothing

• reduce damage from scratching
clothing, bandaging, cut nails

Management of itching
• • • • topical agents gadgets systemic agents psychological interventions

Topical agents
• emollients • antihistamines* - doxepin (Xepin) • unknown mechanism crotamiton (Eurax) calamine • counter-irritant - capsaicin, menthol • local anaesthetics * *Risk sensitization • paste bandages

Management of itching
• • • • topical agents gadgets systemic agents psychological interventions

Management of itching
• • • • topical agents gadgets systemic agents psychological interventions

Systemic agents
• • • • • • • • Antihistamines ? Opiod antagonists Ondansetron Rifampicin Cholestyramine Tricyclic antidepressants Thalidomide Phototherapy

Management of itching
• • • • topical agents gadgets systemic agents psychological interventions

Psychological and alternative interventions
• Biofeedback • Behaviour therapy* • Relaxation techniques • Acupuncture • Hypnotherapy • Homeopathy • Self-help groups *Melin I et al Behavioural treatment of scratching in patients with atopic dermatitis.
Brit J Dermatol 1986; 115: 467-74

Summary
• Itching can be caused by skin disease, systemic disease, psychogenic factors or idiopathic • Management and investigation need to be tailored to the patient’s condition and circumstances


				
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