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.

Features

• 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

Magnified view of a burrowing trail of the scabies mite. The scaly patch on the left was caused by scratching and marks the mite's entry point into the skin. The mite has burrowed to the top-right, where it can be seen as a dark spot at the end. Source: https://en.wikipedia.org/wiki/Scabies

Scabies of the foot. Source: https://en.wikipedia.org/wiki/Scabies

Scabies of the arm.Source: https://en.wikipedia.org/wiki/Scabies

Scabies on the right hand, wrist, and arm. Many itchy red spots are visible. The skin was coated with a soothing lotion (hence its white appearance). Source: https://en.wikipedia.org/wiki/Scabies

Management

• permethrin 5% is first-line
• malathion 0.5% is second-line
• give appropriate guidance on use (see below)
• pruritus persists for up to 4-6 weeks post eradication

Patient guidance on treatment

• avoid close physical contact with others until treatment is complete