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Scratching from A Hard Day’s Night? Meet the beetles!

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By Warren R. Heymann, MD
May 17, 2016

One of my least favorite encounters in dermatology is telling patients that it looks like they have insect bites. The usual responses are: “From what?” “I haven’t been outside,” “My vet says my dog doesn’t have fleas,” “My wife doesn’t have any bites,” “I don’t believe you,” “I’m clean, how can that be?” “I heard you had a good reputation, HA!”

I cannot even imagine how often I’ve recommended that patients get a professional exterminator into their home. Quite frankly, I really know next to nothing about insects (other than the rudimentary lists learned for the boards, forgotten long ago). Other than the “breakfast, lunch, and dinner” pattern of bedbug bites, I am truly an insect ignoramus.

Even when patients take my advice and get an exterminator to assess the home front, I can only recall a rare time or two when insects were actually identified. Patients characteristically tell me that nothing was found. I always wonder about the competency of those doing the inspecting or if patients are just humoring me, when they never complied with the recommendation.

That is why the article by MacArthur et al is so satisfying. They presented a 74 year-old man with papulo-pustular-vesicular lesions that worsened at night. A biopsy demonstrated a spongiotic lesion with an eosinophilic infiltrate, consistent with a bite reaction. Two exterminators identified carpet beetles and treated the home. Between that maneuver, and symptomatic treatment with cetirizine, and triamcinolone he improved. According to the authors the most common beetle genera in the United States are Attagenus megatoma and Anthrenus scrophularieae. The hypersensitivity reaction may be due to the insect blood or their larval hairs (hastae) (1).

According to Hoverson et al, Demestid beetles, particularly carpet beetles, are expected to be in virtually every dwelling worldwide. “Despite the ubiquitous distribution of these common urban pests, most persons do not develop any type of reaction.” In order to actually prove allergy to the insect, patch and prick tests prepared from the larvae can be performed.(2).

So there it is—– another documented reason to encourage patients to get an exterminator in their home when bites are suspected. Good luck!

1. MacArthur KM, et al. Carpet beetle dermatitis: a possibly under-recognized entity. Int J Dermatol 2016: 55: 577-9.
2. Hoverson K, et al. Dermestid dermatitis in a 2 year-old girl: Case report and review of the literature. Pediatr Dermatol 2015; 32: e228-33.

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