On physical examination, the lesions appear to be arthropod bites. The phylum arthropods includes centipedes, millipedes, spiders , scorpions, and insects. The offending biter is difficult to identify without more details from the history, such as whether the individual has any pets (could suggest flea bites), if anyone else in the house has bites (scabies, fleas, or bed bugs), or whether he spent time outdoors with his arms exposed (mosquitoes , outdoor bugs). The distribution of the bites would not be typical of scabies, which tend to appear around the wrists and interdigital spaces. Furthermore, scabies lesions typically feature more extensive excoriation.

Arthropod bites are a significant cause of morbidity worldwide [1]. Arthropod bites and stings cause a range of symptoms in humans, ranging from mildly uncomfortable to life threatening. The majority of arthropod bites cause local reactions; however, some bites can cause toxic and anaphylactic reactions [2]. Many arthropods serve as vectors for diseases such as malaria, dengue, West Nile virus, Rocky Mountain spotted fever, Southern tick-associated rash illness (STARI), and Lyme disease.

The species of concern in the USA include the black widow and brown recluse spiders , the lone star, black-legged (Ixodes scapularis) and dog ticks, bed bugs, fleas , biting flies, and mosquitoes . Their significance is due to prevalence, severity of bite symptoms, or potential to transmit disease [1, 2]. Specifically, black widow spider bites cause severe muscle spasms and brown recluse spider bites can cause skin necrosis. Tick and mosquito bites are common, and the species are vectors for a number of diseases named above.