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Many insects cause mild reactions, such as:

• Bedbugs.
• Kissing bugs.
• Chiggers.
• Fleas.
• Flies.
• Mites.
• Mosquitoes.
• Nonpoisonous spiders.
• Ticks.
• Scabies.
• Lice. For more information on lice, see the topic Lice.

Some insects are more likely than others to cause allergic or toxic reactions.

• A bee leaves the stinger behind and then dies after stinging. Africanized honeybees, the so-called killer bees, are more aggressive than common honeybees and often attack together in great numbers.
• Wasps, including hornets and yellow jackets, can sting over and over. Yellow jackets cause the greatest number of allergic reactions.
• A fire ant attaches to a person by biting with its jaws, then, pivoting its head it stings from its abdomen in a circular pattern at multiple sites.

Bites and stings are more serious if you develop one or more of the following conditions after an insect or spider bite or sting:

• A severe allergic reaction (anaphylaxis)
• A toxic reaction
• A large skin reaction
• Signs of a skin infection
• Serum sickness