Abstract: Methods and immunoassays for diagnosing a bite or sting of a venomous organism in a patient having symptoms consistent with such a bite or sting are provided. A sample of venom is collected from the area of the suspected bite or sting using a swab and then contacted with an antibody that specifically binds to an antigenic site on venom present in the sample. Binding is then detected. The invention is illustrated by examples showing diagnosis of brown recluse spider bite, distinguishing it from other diagnoses with which it is often confused. This extremely sensitive test can detect venom antigens down to about 20 picograms even after the sample has been shipped and stored for periods of up to three weeks during the summer.