Positive and negative examination features for evaluation of possible brown recluse envenomations

Positive exam features	Negative exam features
Lesion has small central blister without pus	Pus observed in lesion
Pale area in center of the lesion	Center raised and red
Purpura/bruising	Drainage present before 1 week*
Purpura spread in a direction consistent with gravity (gravitational spread)	Tender enlarged lymph node present^¶ Ulcer present before 1 week
Outer part of lesion is red and either pale area in center or purpura is present	Ulcer >10 cm in diameter or more than 0.5 cm deep
Central pale area with some surrounding purpura; outer part of lesion is red (red, white, and blue sign)	More than 2 separate lesions Lesion present more than 3 months

* Ignore this negative feature for some body sites: periorbital region, hands, feet.
¶ Adenopathy is observed in approximately 1% of brown recluse spider bite cases.

Reproduced from: Rader RK, Stoecker WV, Malters JM, et al. Seaonality of brown recluse populations is reflected by numbers of brown recluse envenomations. Toxicon 2012; 60:1. Table used with the permission of Elsevier Inc. All rights reserved.

Graphic 94477 Version 3.0

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Positive and negative examination features for evaluation of possible brown recluse envenomations