Toxic reaction: A toxic reaction can cause symptoms
similar to those of an allergic reaction, including nausea, fever, swelling at
the site of the sting, fainting, seizures, shock, and even death. A toxic
reaction occurs when the insect venom acts like a poison in the body and may
result after only one sting, but it usually takes many stings from insects that
are not normally considered poisonous. Spider venom usually causes a toxic
Serum sickness:Serum sickness
is an unusual reaction to a foreign substance in the body. You can have a
delayed reaction to an insect sting that causes serum sickness hours or days
after the sting. Symptoms include fever, joint pain, other flu-like symptoms,
hives. Serum sickness may also be due to an
immune system reaction to the sting. If you develop
serum sickness, you may be at greater risk of developing a severe allergic
reaction to future stings.
Less commonly, bites from certain insects—such as deerflies,
horseflies, kissing bugs, bedbugs, and mosquitoes—can cause allergic reactions. But the reaction from bites is usually more mild than from stings.