Although many different types of insects in the United States are able to inflict a poisonous bite or sting (meaning they are venomous), the insects most likely to cause medical problems are bees (including the domestic honey bee, its Africanized "killer bee" race, and the bumble bee), wasps (including paper wasps, hornets, and yellow jackets), and ants (including the fire ant). These insects are all in the Hymenoptera order, and thus stings from them are occasionally called Hymenoptera stings.
Because many of these species live in colonies, if one stings you, you may be stung by many. Although most stings cause only minor medical problems, some stings may cause serious medical problems and even death.
Allergic reaction: The vast majority of serious medical problems and deaths result from an allergic reaction. This happens in certain people whose immune systems are overly sensitive (or allergic) to the venom. When they get stung, their body may overreact to the venom, and an allergic reaction may happen throughout their body.
These people are frequently described as being allergic to specific insect stings. In the U.S., about 40 deaths are reported each year from insect venom anaphylaxis (severe allergic reaction). These fatal allergic reactions frequently, but not always, occur in people who have had a previous allergic reaction to the same type of insect. Although multiple stings increase the potential danger in allergic cases, a serious or even fatal allergic reaction can (and does) occur from a single sting in a person with no known prior allergic reaction.
The vast majority of serious and fatal allergic reactions from stings cause a significant and obvious allergic reaction within an hour of being stung. Most deaths from stings occur within the first hour. Immediate emergency medical care is critical in known or suspected allergic reactions after an insect sting. In rare cases, serious or even fatal allergic reactions may not happen for up to four or more hours after an insect sting.