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Spider anaphylaxis


Reviewed: February 24, 2020
Patient admitted to ICU with angioedema/urticaria. History stating previous insect bite. No signs of sepsis, redness, streaking. Patient convinced she was bitten by a "brown spider". Developed reaction within 15 minutes of "bite". Review of literature does not show IgE mediated reaction as cause of angioedema. I would appreciate any input on such a case.


The description is consistent with anaphylaxis but the question is whether the triggering event was a spider bite. The circumstances of where the suspected event occurred might be of help since spider bites generally do not occur with normal activities but are generally when investigating undisturbed areas, including undisturbed domestic areas such as stored materials, closets or beneath beds. The most feared “brown” spider, typically encountered in undisturbed areas, is the brown recluse spider. The bite is locally toxic with soft tissue necrosis. Angioedema has been described but not definite anaphylaxis (Dare). Anaphylaxis is seldom reported from any spider, although a suspected reaction to a “huntsman spider” is in the literature (Isbister). Huntsman spiders are found in Southern US and other warm weather areas around the globe. These are extremely large, brown spiders that bite. There are no reports of anaphylaxis to black widow bites but there are at least 2 cases of anaphylaxis from black widow antivenom (Hoyte). Other spiders have caused anaphylaxis in dogs so it is plausible there may be human anaphylaxis.

I would emphasize that the reliability of affected individuals in properly identifying suspect arthropods is suspect at best. I would refer you to a study of hymenoptera stings that showed the identification was unreliable (Baker).

In summary, it is plausible, though unlikely, that a brown spider was responsible for the anaphylaxis. The circumstances of the exposure might help in guessing the possible identity of the culprit spider. It is also possible that the event was misassociated with the spider bite both due to the difficulty in identifying arthropods following an event and the remarkably limited number of reports of spider anaphylaxis despite human exposure to biting spiders. There are no available reagents to my knowledge for testing to spider bites. Finally, the cause of many cases of anaphylaxis is not identified.

Baker, Troy W., et al. "The HIT study: Hymenoptera Identification Test—how accurate are people at identifying stinging insects?" Annals of Allergy, Asthma & Immunology 113.3 (2014): 267-270.

Isbister, Geoffrey K. "Acute allergic reaction following contact with a spider." Toxicon 40.10 (2002): 1495-1497.

Hoyte CO, Cushing TA, Heard KJ. Anaphylaxis to black widow antivenom. Am J Emerg Med 2012;836:e1-2.

Dare, R. K., et al. "Brown recluse spider bite to the upper lip." The Journal of the Arkansas Medical Society 108.10 (2012): 208-210.

Srugo, I., I. Aroch, and Y. Bruchim. "Anaphylactic Reaction to a Spider (Chaetopelma Aegyptiaca) Bite in a Dog." Veterinary Medicine Israel Journal of 7 (2009): 84.

I hope this information is of help to you and your patient.

All my best.
Dennis K. Ledford, MD, FAAAAI