- 1 Introduction
- 2 What are the symptoms?
- 3 Appearance of rash
- 4 How to diagnose?
- 5 What are the treatment options?
- 6 Patient education
- 7 References
Scabies is a parasitic infection due to the mite Sarcoptes scabiei. It is spread from person to person by direct contact (directly touching).
The mite can survive for 24 to 36 hours out of the human body. It is uncommon but possible to catch the infection by touching contaminated linen.
What are the symptoms?
The itch is severe especially at night. It is a body’s reaction to the mite, mite feces and mite eggs (delayed type IV hypersensitivity). Hence, even after successful treatment, the itch can persist.
Appearance of rash
- Sides and webs of fingers
- Flexor aspects of the wrists
- Extensor aspects of elbows
- Axillary folds (anterior, posterior)
- Skin adjacent to nipples
- Periumbilical areas
- Male genitalia
- Extensor surface of knees
- Lower half of buttocks
- Lateral and posterior aspects of feet
- (Back is relatively free of involvement and head is spared except young children)
Thin greyish reddish line 2-15mm long.
Seen more frequent in elderly, downs or other conditions that compromise cellular immunity (lymphoma, AIDS, etc).
Normally starts as poorly defined red patches that quickly become scaly. It might be slightly or even not itchy.
Wheals, vesicles, pustules and rarely bullae.
How to diagnose?
<need to verify with quest lab>
- “Skin scraping for scabies microscopy” (write this on the lab request form). This test is done to identify the mites and eggs.
- Prepare the required equipment:
- Specimen bottle (standard urine bottle)
- Scissors or blade
- Alcohol swab
- Look for an appropriate place to scrape.
- Find a red papule or burrow that has not been scratched preferably.
- Place 2-3 drops of ink over the red papule.
- Leave the ink for 5-10 seconds, then wipe the area with an alcohol swab.
- The ink will seep into the burrow allowing us to identify it better.
- Place a drop of oil on the entire area, then pinch the area and scrape the entire area
- Cover it, label properly and send it to the lab or look under the microscope.
Sticky tape test
Can try using a clear sticky tape to apply over the affected area and send to the lab. <this method has not been tested locally yet: want to try?>
Examination of the skin surface with a special device.
Identification of the “delta-wing” sign.
<picture from https://painepodcast.com/category/dermatology/ , permission to reproduce has not been obtained>
What are the treatment options?
- Topical permathrin 5%
- After the patient bathes, apply to the entire body from neck down.
- Keep and wash off after 8-14 hours.
- If no new rashes after 10 days, no retreatment is required.
- Can use in pregnant women (category B), and infants >2 months old.
- Itch can last up to 4 weeks after successful treatment.
Ivermectin has been proven to be very effective in the treatment of scabies.
200mcg/kg single dose followed by a repeat dose after 1-2 weeks. (I think 1 tablet is 6 or 12mg)
We will use it in large-scale outbreaks in a nursing home or recalcitrant patients.
Decontaminate all linens, towels, and clothing used in the past four days by hot-water washing >60°C and heated drying. Items that cannot be washed in hot water should be dry cleaned or sealed in a plastic bag for five days (to let the mites starve to death).
- Uptodate.com article on Scabies, written by Beth G Goldstein, MDAdam O Goldstein, MD, MPH. Accessed on 29/1/2017
- https://painepodcast.com/category/dermatology/. Picture on the “delta-wing” sign.
- Flinders DC, De Schweinitz P. Pediculosis and scabies. Am Fam Physician 2004;69(2):341–8.
- Gunning K, Pippitt K, Kiraly B, Sayler M. Pediculosis and scabies: treatment update. Am Fam Physician 2012;86(6):535–41.
- Johnstone P, Stong M. Scabies. Am Fam Physician 2015;92(10):919–20.