Scabies

Question 1

What is the cause of scabies?

Answer 1

A skin mite called Sarcoptes scabiei

Question 2

Describe how the itch from scabies works?

Answer 2

The scabies mite burrows into the skin, laying its eggs in the stratum corneum. The intense pruritus associated with scabies is due to a delayed type IV hypersensitivity reaction to mites/eggs which occurs about 30 days after the initial infection.

Question 3

What are some features of scabies?

Answer 3

• Widespread pruritus
• Linear burrows on the side of fingers, interdigital webs and flexor aspects of the wrist
• In infants the face and scalp may also be affected
• Secondary features are seen due to scratching: excoriation, infection

Question 4

How do you manage scabies?

Answer 4

1. Permethrin 5% is first-line
2. Malathion 0.5% is second-line
3. Give appropriate guidance on use (see below)
4. Pruritus persists for up to 4-6 weeks post eradication

Question 5

What patient guidance should be given with treatment?

Answer 5

• Avoid close physical contact with others until treatment is complete
• All household and close physical contacts should be treated at the same time, even if asymptomatic
• Launder, iron or tumble dry clothing, bedding, towels, etc., on the first day of treatment to kill off mites.

Question 6

How does the BNF recommend applying treatment?

Answer 6

• Apply the insecticide cream or liquid to cool, dry skin
• Pay close attention to areas between fingers and toes, under nails, armpit area, creases of the skin such as at the wrist and elbow
• Allow to dry and leave on the skin for 8-12 hours for permethrin, or for 24 hours for malathion, before washing off
• Reapply if insecticide is removed during the treatment period, e.g. If wash hands, change nappy, etc
• Repeat treatment 7 days later

Question 7

Who mainly gets crusted norwegian scabies?

Answer 7

Immunosuppressed and HIV.