Many insects cause mild reactions, such as:

• Mosquitoes.
• Flies.
• Fleas.
• Bedbugs and kissing bugs.
• Chiggers.
• Nonpoisonous spiders.
• Ticks.
• Scabies.
• Lice.
• Mites.

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. These conditions include:

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