Scabies is caused by the mite Sarcoptes scabiei and is spread by prolonged skin contact. It typically affects children and young adults.

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.

Risk factors:

• Overcrowded living conditions
• living in close contact with infected people
• age <15 or >65
• Sexual contact with new or multiple partners
• Immunosuppression
• Poor hygiene

Features

• widespread pruritus
• linear burrows (wavy whitish lines on skin surface) 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

Investigations

• Ectoparasite preparation
  • Should be performed on any patient suspected to have scabies, but should not delay treatment if there is a high index of clinical suspicion.
  • presence of mite, eggs, or faecal material of mites
• Skin biopsy - To look for alternative diagnosis if negative ectoparasite