Dust Mites: Size, Life Cycle & Facts

Instructor: Bryan Cowing

Bryan is a freelance writer who specializes in literature. He has worked as an English instructor, editor and writer for the past 10 years.

Do you or someone you know have dust allergies? Did you know that it might be a reaction to dust mites and not the actual dust? Dust mites are closer to us than we realize. Would you like to learn more?

Introduction and Size

You have probably heard of dust mites, but did you know that they are not insects? Actually, they belong to the Arachnida class, which includes spiders, scorpions, and ticks. Dust mites aren't parasites; they do not bite or even sting. They have eight legs, no eyes and no antennae. The typical dust mite averages 0.2 - 0.3 millimeters in size. You will not be able to spot them with the naked eye. The best way to see these critters is under a microscope, or by using a powerful magnifying glass.

Close up of a house dust mite
House dust mite up close

Gross/Interesting Facts

  • 10% of people are known to have allergic reactions caused by dust mites.
  • The allergy is not to the mite itself, but an enzyme excreted in its feces and from parts of the body that it sheds.
  • Dust mites have eight legs, except while in larva form; then they only have six legs.
  • An average double bed can contain up to ten million dust mites.
  • As we all know, dust mites eat the skin and hair we shed, but they also eat bacteria, fungus and pollen.
  • Dust mites thrive in dark, hot, and humid climates.
  • They also drown quite easily; regularly washing your sheets, pillowcases, curtains, and throws is one effective way to get rid of them.
  • Another great way to exterminate dust mites is by exposing them to direct sunlight.
  • Dust mites are so small and lightweight, that when you make your bed, they get dispersed into the air.
  • The dust mite has hard layer of skin called the exoskeleton. Basically, the skeleton of the creature is on the outside of its body, and forms a protective layer or armor.
  • The average dust mite lives up to three months.
  • 75% of a dust mite is made up of water.
  • Dust mites cannot see, but have a terrific sense of smell. They use this sense to find food and a mate.
  • A 5-year-old pillow can be 50% heavier than a new one because it contains dead mites and excrement.

Life Cycle

Dust mites complete their entire life cycle (from egg to adult) within one month. After they become an adult, they live an additional one to three months. There are four major phases before a dust mite becomes an adult:

  • Egg
  • Larva
  • Protonymph
  • Tritonymph
  • Adult

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