EM Quiz: Treating a rash of problems

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Handling an annoying case of the scratches.  

A 7-year-old girl complains of itching and a rash for the last two to three days. The patient attends public school. Her parents said she has not been camping recently and is acting like her normal self except for constant scratching. Her vital signs are unremarkable, and the only pertinent positive physical exam finding is shown below. What is the next best step in management?


A. Diphenhydramine PO q6h PRN

B. Doxycycline

C. Ivermectin 1% once


D. Ivermectin 200 ug/kg PO once

E. Permethrin shampoo twice

Correct answer: A. Diphenhydramine PO q6h PRN

The patient is suffering from bed bugs, a small, wingless insect that bites the skin and can cause bleeding. Small blood spots on the sheets can be a tell-tale sign. The rash is typically linear, especially in a series of 3, commonly referred to as “breakfast, lunch and dinner” pattern. Management is supportive for the patient including antihistamines for pruritis. The family should call an exterminator and wash everything possible in the house in hot water including sheets, curtains, clothing, etc. A deep clean of any carpet is advised as well.


The source in this patient could be anything from a sleepover to the coat rack at school. A common mechanism is the bugs traveling in suitcases from hotels to homes.

Incorrect answer choices:

Doxycycline (Choice B) is indicated for a variety of tick illnesses such as Rocky Mountain Spotted Fever (RMSF). Classic teaching was that all tetracyclines should be avoided in children because of dental staining. However, the CDC published a practice-changing article in 2015 advocating use of doxycycline for appropriate tick-borne illnesses in children in the context of finding no visible dental staining. RMSF starts in the extremities and moves inward to the trunk, the opposite of this rash, so doxycycline is not indicated in this case. Additionally, RMSF can include the palms and soles.

Topical (Choice C) and oral (Choice D) ivermectin are helpful one-time medications for several ectoparasites. Oral ivermectin safety is not characterized in children less than 15kg, so topical ivermectin should be used for them instead. Topical ivermectin is indicated for head lice and scabies. Oral ivermectin is indicated for scabies.

Permethrin shampoo (Choice E) is indicated for head lice, genital lice and scabies. It is applied once, then again one week later. This patient does not complain of head or genital itching. The scabies rash more classically presents on the hands, and the bug is sometimes visible with a magnifying glass under the skin, burrowed.


Schneir A, Clark RF. Chapter 211: Bites and Stings. In: Tintinalli JE, Stapczynski J, Ma O, Yealy DM, Meckler GD, Cline DM. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e New York, NY: McGraw-Hill; 2016.

Todd SR, Dahlgren FS, Traeger MS, et al. No visible dental staining in children treated with doxycycline for suspected Rocky Mountain Spotted Fever. J Peds. 2015;166(5):1246-1251.


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