An arthropod bite or sting may develop a localized inflammatory reaction manifested by localized swelling, redness, pain, burning, and pruritus.

Reactions may be more pronounced in the immunocompromised patient. An exaggerated, sometimes bullous reaction to an arthropod bite is characteristic of certain immunosuppressed states, especially a hematopoietic malignancy or HIV disease. In HIV-infected individuals, arthropod assaults may result in an extremely pruritic skin eruption called "pruritic papular eruption."

Arthropods include insects (stinging or venomous hymenoptera [eg, bees, wasps, fire ants] and non-venomous insects [eg, mosquitoes, fleas]) as well as ticks, mites, spiders, scabies, and body lice. Other arthropods often remain unidentified.

Arthropods may transmit human illness (including tick bite fever, Lyme disease, Rocky Mountain spotted fever, a variety of encephalitides, malaria). Venomous bites may trigger systemic toxic or allergic reactions, including anaphylaxis. An ascending paralysis caused by a neurotoxin may occur after a tick bite.

Some arthropod infestations, such as pediculosis capitis, scabies and crusted scabies, are highly contagious and pose a particular problem in the institutional setting.

There are highly variable global distributions of insects and arthropods. In returning travelers, insect bites are the fourth most common skin complaint diagnosed.