Insect bites and stings occur when an
insect is agitated and seeks to
defend itself through its natural defense mechanisms, or when an insect seeks to feed off the bitten person. Some insects inject
formic acid, which can cause an immediate skin reaction often resulting in redness and swelling in the injured area. Stings from
fire ants,
bees,
wasps and
hornets are usually
painful, and may stimulate a dangerous
allergic reaction called
anaphylaxis for at-risk patients, and some wasps can also have a powerful bite along with a sting. Bites from
mosquitoes and
fleas are more likely to cause
itching than pain.