Scabies Flashcards
General history
In frail elderly in rest homes, infestations can spread rapidly so a high index of suspicion is vital.
Consider any rash affecting more than one person (residents or staff) as scabies until proven otherwise.
- Previous episodes
- Duration i.e., when any issues were first noticed
- Hx of eczema or other skin problems in pt or family
- Allergies
- Bite wounds
- Other symptoms e.g., fever
- Any current oral or topical medications or lotions applied to the skin
- Any other family members, or friends
Key features
An intensely itchy rash made worse by heat e.g., after showering or in bed
Contact with another itchy person
Rash in typical scabies sites
Scabies sites
- Usually on hands finger web spaces, and wrists
- Common on male genitalia
- Also on outer elbows, axillae, sides or soles of the feet, nipples of females
Allergic hypersensitivity reaction from a mite
Can be found on any part of the body and is not necessarily where the mite actually is.
The rash does not usually affect the scalp or face, except in babies, the bed-bound, or debilitated patients.
Examine the patient’s skin:
Look for a rash with scratch marks, which may involve;
- papules
- nodules
- or excoriations.
Use a low-level magnifier to look for burrows or tracks
Dermoscopy as this can be diagnostic.
- Microscopic examination of the contents of a burrow may reveal mites, eggs, or mite faeces (faecalith).
Risk factors
Living in lower socio-economic area
Settings with high levels of population density e.g.:
- overcrowded housing
- institutional care e.g., rest homes, hospitals, prisons
- refugee camps
Immunocompromised patients
Investigation
Usually diagnosed clinically.
If a generalised scaly rash with very little itch, consider crusted scabies.
Laboratory diagnosis by skin scraping has low sensitivity.
Differential diagnoses
Flea and bug bites:
- Look at bite welts, characteristically 3 in a row adjacent to hem lines, ankles, belt line, and arms for fleas.
- Advise pt to check sheets at 3.00 am for the apple seed-sized bed bugs which do not like light.
Infections, including viral exanthema, eczema, and contact dermatitis
Allergic reactions e.g., papular urticaria
Immunologically mediated diseases e.g., bullous pemphigoid and pityriasis rosea
General management
Start drug treatment.
Manage the itch.
Discuss the importance of environmental decontamination.
Provide written instructions and stress the importance of complying with Ry.
Drug treatment
A). Classical scabies:
- Topically with 5% permethrin lotion or cream (2 doses, on day 0 and day 7).
- or Benzyl benzoate 25% emulsion (dilute 50:50 with water if under 10 yrs; if <2 yrs dilute 1:3)
- Follow application instructions.
- Treat pts who are physically or mentally unable to complete topical treatment with oral ivermectin.
B). Norwegian / Crusted scabies –https://dermnetnz.org/topics/crusted-scabies
- Requires combined oral and topical treatment:
- Oral ivermectin (200 micrograms/kg/dose) given on days 1, 2, 8, 9, and 15. Add days 22 and 29 if infestation is severe.
- Combine with topical 5% permethrin applied daily for 7 days, then twice a week until cured.
- If required, salicylic acid 5 to 10% in sorbolene cream can also be applied to crusted areas to decrease crusting and improve absorption of permethrin.
How to manage the itch?
Oral antihistamines
Emollients
Mild to moderate topical corticosteroids
Itch-Soothe crotamiton cream 10% and calamine lotion
A topical antipruritic (e.g. crotamiton cream) can be used for persistent itch (usu. up to 3 wks)
Environmental decontamination
All bedding and towels must be stripped and hot washed and hot dried
The mite is not small enough to go through the weave of sheets, so the mattress and any mattress protectors do not require laundering.
Contaminated clothing must be decontaminated using:
- hot wash and dry as above, or
- dry clean, or
- seal in a plastic bag for 7 days at room temperature, or
- seal in a plastic bag and freeze overnight.
Follow up
Wait at least 2 to 3 weeks after initial treatment, then check for new lesions.
The rash often lasts for over 6 weeks, making cure difficult to assess.
The itch may persist for weeks even when the mite has gone – provide symptomatic relief if required.
If any Ry failure, ask about adherence to medication, application process, and environmental decontamination.
If signs and symptoms persist 6 weeks after treatment
Discuss the method of permethrin application
Confirm compliance with treatment, and that all household members were treated.
If incorrect process was used, repeat Ry
If correct process used, seek dermatology advice.
If there is secondary cellulitis or impetigo, consider oral antibiotics.
Request
Healthy Homes Initiatives (HHIs):
Free services, aims to help families have warmer, drier, and healthier homes through education and access to interventions.
They work in partnership with the family and are supported by social work and inter‑agency collaboration.
