Photo Rounds

Large leg rash

A young woman presented to her family physician with a large rash on her leg that she’d had for 2 weeks. She said that she’d gotten a bug bite in the area 3 weeks earlier, but didn’t know how the rash came about. Her mother had given her an antibiotic ointment to put on the bug bite. The woman was otherwise in good health.

What’s your diagnosis?


The family physician (FP) asked some more questions about the antibiotic ointment and discovered that it was a triple antibiotic ointment (which typically contains neomycin, bacitracin, and polymyxin). The patient acknowledged that after applying the ointment to the bug bite, she’d used a bandage that was rectangular in shape—just like the patch of erythematous skin with papules.

The FP deduced that this was a case of contact dermatitis and the patient was reacting to at least one of the topical antibiotics in the triple antibiotic preparation. The most likely offending topical antibiotic was neomycin, as it’s a common contact allergen. However, bacitracin is also a common contact allergen.

The FP told the patient to stop using the triple antibiotic ointment and to avoid using any preparations that contain neomycin, bacitracin—or both—in the future. The FP explained that most minor skin injuries, including bug bites and minor scrapes, do not require topical antibiotics.

The FP prescribed 0.1% triamcinolone cream to be applied twice daily to treat the erythema and itching caused by the contact dermatitis. At a follow-up visit one month later, the only skin problem that persisted was some postinflammatory hyperpigmentation. The FP explained that this would likely fade over time.

Photos and text for Photo Rounds Friday courtesy of Richard P. Usatine, MD. This case was adapted from: Usatine R. Contact dermatitis. In: Usatine R, Smith M, Mayeaux EJ, et al, eds. Color Atlas of Family Medicine. 2nd ed. New York, NY: McGraw-Hill; 2013:591-596.

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