Paediatrics: Pruritus

Pruritus

Is the sensation provoking a desire to scratch? If severe, it leads to excoria-tion, papules or nodules (localized skin thickening), and lichenification.

Generalized pruritus

Causes

·  Skin diseases (see Localized pruritus, p.820).

·  Hepatic disease (bile salts).

·  Food or drug reaction/allergy (e.g. penicillin).

·  Underlying malignancy, particularly lymphoma.

·  Chronic renal failure.

·  Hypo- or hyperthyroidism.

·  Parasites (e.g. scabies).

·  Iron deficiency anaemia.

Investigation

In absence of obvious underlying skin disease:

·  FBC.

·  Blood film.

·  CRP/ESR.

·  Ferritin.

·  LFT.

·  U&E and creatinine.

·  Glucose.

·  TFT.

Treatment

·  Treat causative disease.

·  Bland topical emollients.

·  Emollient bath oils.

·  Night-time sedative, e.g. antihistamines.

Localized pruritus

Causes

·  Atopic eczema (cheeks, hands, and limb flexures).

·  Contact dermatitis.

·  Urticaria.

·  Insect bites.

·  Fungal infection (e.g. tinea capitis).

·  Head lice (pediculosis capitis).

·  Scabies (finger webs, wrists, groin, buttocks).

·  Psoriasis.

·  Dermatitis herpetiformis (elbows, shoulders, genitalia, perineum, buttocks).

·  Pityriasis rosea.

·  Chickenpox.

Dermatitis artefacta (!).

Investigation 

In absence of obvious underlying skin disease, investigate as for generalized pruritus.

Treatment 

As for generalized pruritis.

Pruritus ani

Localized peri-anal itching.

Causes

·Threadworms.

·Anal disease (e.g. anal fissure, haemorrhoids, Crohn’s disease).

·Poor hygiene.

·Chronic faecal soiling.

·Chronic diarrhoea.

·Localized skin disease (e.g. candidiasis, psoriasis).

·Contact dermatitis (e.g. to toilet paper).

·Idiopathic.

Investigation 

Threadworms may be seen during anal inspection or their eggs seen on microscopy of ‘sellotape’ applied to the anus or skin swab culture.

Treatment

·Treat underlying disease.

·Improve perianal hygiene.

·Mild topical steroid may relieve once infective cause is excluded.

Pruritus vulvae

Localized perivulval itching.

Causes

·Idiopathic.

·Poor hygiene.

·Infection (e.g. candidiasis, trichomoniasis).

·Diabetes mellitus.

·Threadworm.

·Contact dermatitis.

·Localized skin disease (see pruritus ani), e.g. lichen sclerosus.

Treatment 

As for pruritus ani.