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31 May 2024

Causative agent

Scabies is a skin disease caused by the mite Sarcoptes scabiei var. hominis, which is a parasite that burrows into, resides and reproduces in human skin. It affects people of all ages, but the elderly or people with weakened immunity are more susceptible. Scabies can spread rapidly in crowded conditions, hence outbreaks of scabies have been reported in institutional settings such as hospitals, child-care facilities, hostels and elderly homes.

Clinical features

The most common symptom of scabies is intense itchiness which is more severe at night. Rashes, thread-like lesions or vesicles may also be seen on the skin. Scratching the rash may lead to bacterial skin infections, such as impetigo. The commonly affected areas for people with scabies are finger webs, wrists, elbows, armpits, nipples, lower abdomen, external genitalia, buttocks and shoulder blades. The face, scalp, neck, palms of the hands and soles of the feet are usually spared, except in infants, young children and immunocompromised persons.

A severe form of scabies known as Norwegian or crusted scabies can occur in the elderly, people with weakened immunity or disabilities. The skin lesions appear as marked scales and crusts, which contain large number of scabies mites and eggs. However, persons with crusted scabies may not show the usual signs and symptoms of scabies such as rash and itchiness. This type of scabies is highly contagious because an infested person may harbour thousands of mites, compared to 10 to 15 mites in typical scabies.

Mode of transmission

Scabies usually spreads through direct skin contact with an infested person. Items, such as clothing, bed linen and towels, contaminated by an infested person may also carry the mites or eggs and transmit the disease. However, such indirect spread of scabies may occur much more easily for individuals with crusted scabies. Transmission within household and institutional settings is common.

Incubation period

Incubation period is usually about 4 to 8 weeks for people with new infestation. For people who have previously been infested with scabies, symptoms develop sooner, usually within 1 to 4 days after re-exposure. Infested people can spread scabies even if they have no symptoms.


  • If you suspect scabies, seek medical advice immediately.
  • Apply topical medicated lotions and take medications according to the doctor's advice to kill the mites and control itchiness respectively. Antiseptics or antibiotics may be necessary to treat bacterial skin infections.
  • Family member(s), sexual partner(s) and close personal contacts of the infested persons are recommended to seek medical advice and receive treatment in order to reduce spread of the disease.
  • When caring for and coming into contact with the infested persons, wear appropriate personal protective gear such as gloves and gown.
  • Wash hands thoroughly before and after contact with the infested person. Wash hands with liquid soap and water, and rub for at least 20 seconds. Then rinse with water and dry with a disposable paper towel or hand dryer.
  • Wash the clothing, bed linen and towels of the infested persons separately, so as to kill the mites and their eggs. The contaminated items should be washed in hot water at 60°C or above for not less than 10 minutes, and dried in direct sunlight, a hot dryer cycle or dry cleaning. Place non-washable items in a sealed plastic bag for at least 7 days before reuse.
  • Dedicated use of equipment/ devices for infested person is recommended.
  • Clean shared equipment/ devices with detergent before using on other persons.
  • Discard shared use or suspected contaminated creams and lotions.


  • Keep good personal hygiene, perform hand hygiene frequently and daily bathing.
  • Regularly change into clean clothing, bed linen and towels.
  • Avoid sharing clothing and personal items with others.
  • Perform skin inspection for institutionalised residents regularly for early identification of infestation.
  • Thoroughly clean and vacuum furniture and carpets in rooms, especially for those used by people with crusted scabies.