Bumblebees (genus Bombus) are found worldwide, typically in higher latitudes that range from warm to cold climates. Approximately 45 species exist in North America and about 160 species in other parts of the world.

They are relatives of the honeybees but are larger, much more hairy, and characterized by distinct yellow or white bands on their abdomen. Bumblebees are social bees that live in smaller colonies than honeybees. Most species are docile, but queen and worker bees will sting in self defense or when their nest is disturbed. Unlike the honeybee, the stinger is not barbed and does not get stuck in the skin. Therefore, bumblebees can sting more than once.

Bumblebee venom is similar to honeybee venom, and there is cross-reactivity. Bumblebee venom contains phospholipase A2, serine protease, hyaluronidase, acid phosphatase, and several allergens not found in honeybees.

Bumblebee anaphylaxis is rare compared to stings from wasps, hornets, and honeybees due to their docile nature. People at highest risk are those who are occupationally exposed to bumblebees, such as gardeners who use bumblebees for pollination, scientists, and bumblebee breeders. Some individuals are sensitized to bumblebee venom, while others are sensitized to honeybee venom and then develop an allergic reaction to a bumblebee sting due to cross-reactivity.

Local bumblebee sting reactions include immediate pain, swelling, and redness at the sting site that often subsides within a few hours.

Regional reactions (exaggerated local reactions) occur in some individuals with extended swelling that can last 2-7 days. These reactions are not allergic in origin.

Anaphylactic reactions cause diffuse urticaria, pruritus, angioedema, bronchoconstriction, respiratory distress, hypotension, loss of consciousness, and cardiac arrhythmias. Typically, anaphylactic signs occur within 10 minutes of the sting.