‘An unpleasant sensation, which provokes a desire to scratch’.

Pathophysiology

• Arises in skin, conjunctivae and mucous membranes.
• Can be classified as:
  • Cutaneous – arises from skin.
  • Neuropathic – damage to nerves or by direct irritation.
  • Psychological.
• Transmitted through C fibres (similar to pain).
• Receptors are more superficial than pain receptors.
• Fibres respond to pruritogens including histamine, acetylcholine and peripheral serotonin.
• Pruritus increases with heat, anxiety and boredom.

Causes

• Opioids – particularly can cause pruritus, and this is more common in children than adults.
• Drugs – many drugs can cause problems but particularly antibiotics (penicillin) and antiepileptics (phenytoin).
• Eczema or dry skin.
• Scabies or lice.
• Renal failure.
• Hepatic disease causing jaundice.
• Haematological disorders particularly leukaemias and lymphomas.
• AIDS.
• Psychological.

Management

• Look at the possible causes and treat appropriately.
• Simple rehydration of the skin with moisturisers.
• Cut back nails, consider the use of mittens.
• Pruritus decreases with cold, distraction and relaxation.
• Keep the child cool.
• Wear loose fitting cotton clothes.
• Calamine lotion.
• If the skin is inflamed then use mild steroid creams such as hydrocortisone.
• Oral corticosteroids can be used if the skin is very inflamed or for pruritus in terminal Hodgkin’s lymphoma.
• NSAIDs can help by reducing prostaglandins, which can sensitise nerve endings to pruritogenic substances.
• H₁ antihistamines are used extensively in most types of pruritus but there will be occasions when they are poorly effective or completely ineffective.
• Serotonin antagonist (e.g. Ondansetron) can relieve some types of opioid induced and cholestatic pruritus.