Papular urticaria is a common pruritic hypersensitivity reaction to the bites of insects of many different types, including fleas, mosquitoes, chiggers, and, more rarely, avian or rodent mites. Which particular insect is the cause varies with geographic location. In San Francisco, children with papular urticaria due to flea bites are part of dermatologic practice year round. With its relatively warm winters and wet, foggy summers, San Francisco is an environment where fleas thrive, and their bites afflict children at day care centers and park playgrounds, as well as in homes with pets. We review the clinical approach to papular urticaria in general, and focus on flea bite prevention and management.